1.
Leonardo D. Machado Cristiano F. Woellner, Pedro A. S. Autreto
The Influence of Morphology on the Charge Transport in Two-Phase Disordered Organic Systems Journal Article
Em: Mater. Res. Soc. Symp. Proc., vol. 1737, 2015.
@article{Woellner2015,
title = {The Influence of Morphology on the Charge Transport in Two-Phase Disordered Organic Systems},
author = {Cristiano F. Woellner, Leonardo D. Machado, Pedro A. S. Autreto, Jose A. Freire, Douglas S. Galvao},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9707375&fulltextType=RA&fileId=S1946427415005023},
doi = {10.1557/opl.2015.502},
year = {2015},
date = {2015-05-22},
journal = {Mater. Res. Soc. Symp. Proc.},
volume = {1737},
abstract = {In this work we use a three-dimensional Pauli master equation to investigate the charge carrier mobility of a two-phase system, which can mimic donor-acceptor and amorphous- crystalline bulk heterojunctions. Our approach can be separated into two parts: the morphology generation and the charge transport modeling in the generated blend. The morphology part is based on a Monte Carlo simulation of binary mixtures (donor/acceptor). The second part is carried out by numerically solving the steady-state Pauli master equation. By taking the energetic disorder of each phase, their energy offset and domain morphology into consideration, we show that the carrier mobility can have a significant different behavior when compared to a one-phase system. When the energy offset is non-zero, we show that the mobility electric field dependence switches from negative to positive at a threshold field proportional to the energy offset. Additionally, the influence of morphology, through the domain size and the interfacial roughness parameters, on the transport was also investigated.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this work we use a three-dimensional Pauli master equation to investigate the charge carrier mobility of a two-phase system, which can mimic donor-acceptor and amorphous- crystalline bulk heterojunctions. Our approach can be separated into two parts: the morphology generation and the charge transport modeling in the generated blend. The morphology part is based on a Monte Carlo simulation of binary mixtures (donor/acceptor). The second part is carried out by numerically solving the steady-state Pauli master equation. By taking the energetic disorder of each phase, their energy offset and domain morphology into consideration, we show that the carrier mobility can have a significant different behavior when compared to a one-phase system. When the energy offset is non-zero, we show that the mobility electric field dependence switches from negative to positive at a threshold field proportional to the energy offset. Additionally, the influence of morphology, through the domain size and the interfacial roughness parameters, on the transport was also investigated.
2.
Autreto, Pedro A. S.; Galvao, Douglas S.
Site Dependent Hydrogenation in Graphynes: A Fully Atomistic Molecular Dynamics Investigation Journal Article
Em: Mater. Res. Soc. Symp. Proc. , vol. 1726 , 2015.
@article{Autreto2015,
title = {Site Dependent Hydrogenation in Graphynes: A Fully Atomistic Molecular Dynamics Investigation},
author = {Pedro A. S. Autreto and Douglas S. Galvao},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=9702693&fulltextType=RA&fileId=S1946427415004649},
doi = {10.1557/opl.2015.464},
year = {2015},
date = {2015-05-22},
journal = {Mater. Res. Soc. Symp. Proc. },
volume = {1726 },
abstract = {Graphyne is a generic name for a carbon allotrope family of 2D structures, where acetylenic groups connect benzenoid rings, with the coexistence of sp and sp2 hybridized carbon atoms. In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the hydrogenation of α, β, and γ graphyne forms. Our results showed that the existence of different sites for hydrogen bonding, related to single and triple bonds, makes the process of incorporating hydrogen atoms into graphyne membranes much more complex than the graphene ones. Our results also show that hydrogenation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. In our cases, the effectiveness of the hydrogenation (estimated from the number of hydrogen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphyne is a generic name for a carbon allotrope family of 2D structures, where acetylenic groups connect benzenoid rings, with the coexistence of sp and sp2 hybridized carbon atoms. In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the hydrogenation of α, β, and γ graphyne forms. Our results showed that the existence of different sites for hydrogen bonding, related to single and triple bonds, makes the process of incorporating hydrogen atoms into graphyne membranes much more complex than the graphene ones. Our results also show that hydrogenation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. In our cases, the effectiveness of the hydrogenation (estimated from the number of hydrogen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering.
3.
Lagos, MJ; Autreto, PAS; Bettini, J; Sato, F; Dantas, SO; Galvao, DS; Ugarte, D
Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains Journal Article
Em: Journal of Applied Physics, vol. 117, não 9, pp. 094301, 2015.
@article{Lagos2015,
title = {Surface effects on the mechanical elongation of AuCu nanowires: De-alloying and the formation of mixed suspended atomic chains},
author = {Lagos, MJ and Autreto, PAS and Bettini, J and Sato, F and Dantas, SO and Galvao, DS and Ugarte, D},
url = {http://scitation.aip.org/content/aip/journal/jap/117/9/10.1063/1.4913625},
year = {2015},
date = {2015-01-01},
journal = {Journal of Applied Physics},
volume = {117},
number = {9},
pages = {094301},
publisher = {AIP Publishing},
abstract = {We report here an atomistic study of the mechanical deformation of Au x Cu (1− x ) atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report here an atomistic study of the mechanical deformation of Au x Cu (1− x ) atomic-size wires (nanowires (NWs)) by means of high resolution transmission electron microscopy experiments. Molecular dynamics simulations were also carried out in order to obtain deeper insights on the dynamical properties of stretched NWs. The mechanical properties are significantly dependent on the chemical composition that evolves in time at the junction; some structures exhibit a remarkable de-alloying behavior. Also, our results represent the first experimental realization of mixed linear atomic chains (LACs) among transition and noble metals; in particular, surface energies induce chemical gradients on NW surfaces that can be exploited to control the relative LAC compositions (different number of gold and copper atoms). The implications of these results for nanocatalysis and spin transport of one-atom-thick metal wires are addressed.
4.
Ozden, Sehmus; Autreto, Pedro AS; Tiwary, Chandra Sekhar; Khatiwada, Suman; Machado, Leonardo; Galvao, Douglas S; Vajtai, Robert; Barrera, Enrique V; M. Ajayan, Pulickel
Unzipping Carbon Nanotubes at High Impact Journal Article
Em: Nano letters, vol. 14, não 7, pp. 4131–4137, 2014.
@article{ozden2014unzipping,
title = {Unzipping Carbon Nanotubes at High Impact},
author = {Ozden, Sehmus and Autreto, Pedro AS and Tiwary, Chandra Sekhar and Khatiwada, Suman and Machado, Leonardo and Galvao, Douglas S and Vajtai, Robert and Barrera, Enrique V and M. Ajayan, Pulickel},
url = {http://pubs.acs.org/doi/abs/10.1021/nl501753n},
year = {2014},
date = {2014-01-01},
journal = {Nano letters},
volume = {14},
number = {7},
pages = {4131--4137},
publisher = {American Chemical Society},
abstract = {The way nanostructures behave and mechanically respond to high impact collision is a topic of intrigue. For anisotropic nanostructures, such as carbon nanotubes, this response will be complicated based on the impact geometry. Here we report the result of hypervelocity impact of nanotubes against solid targets and show that impact produces a large number of defects in the nanotubes, as well as rapid atom evaporation, leading to their unzipping along the nanotube axis. Fully atomistic reactive molecular dynamics simulations are used to gain further insights of the pathways and deformation and fracture mechanisms of nanotubes under high energy mechanical impact. Carbon nanotubes have been unzipped into graphene nanoribbons before using chemical treatments but here the instability of nanotubes against defect formation, fracture, and unzipping is revealed purely through mechanical impact.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The way nanostructures behave and mechanically respond to high impact collision is a topic of intrigue. For anisotropic nanostructures, such as carbon nanotubes, this response will be complicated based on the impact geometry. Here we report the result of hypervelocity impact of nanotubes against solid targets and show that impact produces a large number of defects in the nanotubes, as well as rapid atom evaporation, leading to their unzipping along the nanotube axis. Fully atomistic reactive molecular dynamics simulations are used to gain further insights of the pathways and deformation and fracture mechanisms of nanotubes under high energy mechanical impact. Carbon nanotubes have been unzipped into graphene nanoribbons before using chemical treatments but here the instability of nanotubes against defect formation, fracture, and unzipping is revealed purely through mechanical impact.
5.
Autreto, PAS; de Sousa, JM; Galvao, DS
Site-dependent hydrogenation on graphdiyne Journal Article
Em: Carbon, vol. 77, pp. 829–834, 2014.
@article{Autreto2014,
title = {Site-dependent hydrogenation on graphdiyne},
author = {Autreto, PAS and de Sousa, JM and Galvao, DS},
url = {http://www.sciencedirect.com/science/article/pii/S0008622314005429},
year = {2014},
date = {2014-01-01},
journal = {Carbon},
volume = {77},
pages = {829--834},
publisher = {Pergamon},
abstract = {Graphene is one of the most important materials in science today due to its unique and remarkable electronic, thermal and mechanical properties. However in its pristine state, graphene is a gapless semiconductor, what limits its use in transistor electronics. In part due to the revolution created by graphene in materials science, there is a renewed interest in other possible graphene-like two-dimensional structures. Examples of these structures are graphynes and graphdiynes, which are two-dimensional structures, composed of carbon atoms in sp2 and sp-hybridized states. Graphdiynes (benzenoid rings connecting two acetylenic groups) were recently synthesized and some of them are intrinsically nonzero gap systems. These systems can be easily hydrogenated and the relative level of hydrogenation can be used to tune the band gap values. We have investigated, using fully reactive molecular dynamics (ReaxFF), the structural and dynamics aspects of the hydrogenation mechanisms of graphdiyne membranes. Our results showed that the hydrogen bindings have different atom incorporation rates and that the hydrogenation patterns change in time in a very complex way. The formation of correlated domains reported to hydrogenated graphene is no longer observed in graphdiyne cases.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene is one of the most important materials in science today due to its unique and remarkable electronic, thermal and mechanical properties. However in its pristine state, graphene is a gapless semiconductor, what limits its use in transistor electronics. In part due to the revolution created by graphene in materials science, there is a renewed interest in other possible graphene-like two-dimensional structures. Examples of these structures are graphynes and graphdiynes, which are two-dimensional structures, composed of carbon atoms in sp2 and sp-hybridized states. Graphdiynes (benzenoid rings connecting two acetylenic groups) were recently synthesized and some of them are intrinsically nonzero gap systems. These systems can be easily hydrogenated and the relative level of hydrogenation can be used to tune the band gap values. We have investigated, using fully reactive molecular dynamics (ReaxFF), the structural and dynamics aspects of the hydrogenation mechanisms of graphdiyne membranes. Our results showed that the hydrogen bindings have different atom incorporation rates and that the hydrogenation patterns change in time in a very complex way. The formation of correlated domains reported to hydrogenated graphene is no longer observed in graphdiyne cases.
6.
Vinod, Soumya; Tiwary, Chandra Sekhar; da Silva Autreto, Pedro Alves; Taha-Tijerina, Jaime; Ozden, Sehmus; Chipara, Alin Cristian; Vajtai, Robert; Galvao, Douglas S; Narayanan, Tharangattu N; Ajayan, Pulickel M
Low-density three-dimensional foam using self-reinforced hybrid two-dimensional atomic layers Journal Article
Em: Nature communications, vol. 5, 2014.
@article{Vinod2014,
title = {Low-density three-dimensional foam using self-reinforced hybrid two-dimensional atomic layers},
author = {Vinod, Soumya and Tiwary, Chandra Sekhar and da Silva Autreto, Pedro Alves and Taha-Tijerina, Jaime and Ozden, Sehmus and Chipara, Alin Cristian and Vajtai, Robert and Galvao, Douglas S and Narayanan, Tharangattu N and Ajayan, Pulickel M},
url = {http://www.nature.com/ncomms/2014/140729/ncomms5541/full/ncomms5541.html},
year = {2014},
date = {2014-01-01},
journal = {Nature communications},
volume = {5},
publisher = {Nature Publishing Group},
abstract = {Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. It is found that domains of h-BN layers on the graphene oxide framework help to reinforce the 2D structural units, providing the observed improvement in mechanical integrity of the 3D foam structure.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. It is found that domains of h-BN layers on the graphene oxide framework help to reinforce the 2D structural units, providing the observed improvement in mechanical integrity of the 3D foam structure.
7.
Gao, Guanhui; Mathkar, Akshay; Martins, Eric Perim; Galv ao, Douglas S; Gao, Duyang; da Silva Autreto, Pedro Alves; Sun, Chengjun; Cai, Lintao; Ajayan, Pulickel M
Designing nanoscaled hybrids from atomic layered boron nitride with silver nanoparticle deposition Journal Article
Em: Journal of Materials Chemistry A, vol. 2, não 9, pp. 3148–3154, 2014.
@article{gao2014designing,
title = {Designing nanoscaled hybrids from atomic layered boron nitride with silver nanoparticle deposition},
author = {Gao, Guanhui and Mathkar, Akshay and Martins, Eric Perim and Galv~ao, Douglas S and Gao, Duyang and da Silva Autreto, Pedro Alves and Sun, Chengjun and Cai, Lintao and Ajayan, Pulickel M},
url = {http://pubs.rsc.org/en/Content/ArticleLanding/2014/TA/c3ta12892j#!divAbstract},
year = {2014},
date = {2014-01-01},
journal = {Journal of Materials Chemistry A},
volume = {2},
number = {9},
pages = {3148--3154},
publisher = {Royal Society of Chemistry},
abstract = {We have developed a microwave assisted one-pot approach to fabricate a novel hybrid nano-composite composed of two-dimensional chemically exfoliated layered hexagonal boron nitride (h-BN) and embedded silver nanoparticles (SNP). Atomic layered h-BN exfoliated using chemical liquid showed strong in-plane bonding and weak van der Waals interplanar interactions, which is utilized for chemically interfacing SNP, indicating their ability to act as excellent nano-scaffolds. The SNP/h-BN optical response, in particular band gap, is strongly dependent on the concentration of the metallic particles. In order to gain further insight into this behavior we have also carried out ab initio density functional theory (DFT) calculations on modeled structures, demonstrating that the bandgap value of SNP/h-BN hybrids could be significantly altered by a small percentage of OH− groups located at dangling B and N atoms. Our results showed that these novel SNP/h-BN nanohybrid structures exhibited excellent thermal stability and they are expected to be applied as devices for thermal oxidation-resistant surface enhanced Raman spectroscopy (SERS). The SNP/h-BN membrane showed remarkable antibacterial activity, suggesting their potential use in water disinfection and food packaging.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have developed a microwave assisted one-pot approach to fabricate a novel hybrid nano-composite composed of two-dimensional chemically exfoliated layered hexagonal boron nitride (h-BN) and embedded silver nanoparticles (SNP). Atomic layered h-BN exfoliated using chemical liquid showed strong in-plane bonding and weak van der Waals interplanar interactions, which is utilized for chemically interfacing SNP, indicating their ability to act as excellent nano-scaffolds. The SNP/h-BN optical response, in particular band gap, is strongly dependent on the concentration of the metallic particles. In order to gain further insight into this behavior we have also carried out ab initio density functional theory (DFT) calculations on modeled structures, demonstrating that the bandgap value of SNP/h-BN hybrids could be significantly altered by a small percentage of OH− groups located at dangling B and N atoms. Our results showed that these novel SNP/h-BN nanohybrid structures exhibited excellent thermal stability and they are expected to be applied as devices for thermal oxidation-resistant surface enhanced Raman spectroscopy (SERS). The SNP/h-BN membrane showed remarkable antibacterial activity, suggesting their potential use in water disinfection and food packaging.
8.
Perim Martins, Eric; Paupitz, Ricardo; Autreto, Pedro Alves da Silva; Galvao, Douglas Soares
Inorganic Graphenylene: A Porous Two-Dimensional Material with Tunable Band Gap Journal Article
Em: The Journal of Physical Chemistry C, vol. 118, não 41, pp. 23670–23674, 2014.
@article{perim2014inorganic,
title = {Inorganic Graphenylene: A Porous Two-Dimensional Material with Tunable Band Gap},
author = {Perim Martins, Eric and Paupitz, Ricardo and Autreto, Pedro Alves da Silva and Galvao, Douglas Soares},
url = {http://pubs.acs.org/doi/abs/10.1021/jp502119y},
year = {2014},
date = {2014-01-01},
journal = {The Journal of Physical Chemistry C},
volume = {118},
number = {41},
pages = {23670–23674},
publisher = {American Chemical Society},
abstract = {By means of ab initio calculations, we investigate the possibility of existence of a boron nitride (BN) porous two-dimensional nanosheet, which is geometrically similar to the carbon allotrope known as biphenylene carbon. The proposed structure, which we called inorganic graphenylene (IGP), is formed spontaneously after selective dehydrogenation of the porous boron nitride (BN) structure proposed by Ding et al. We study the structural and electronic properties of both porous BN and IGP, and it is shown that, by selective substitution of B and N atoms with carbon atoms in these structures, the band gap can be significantly reduced, changing their behavior from insulators to semiconductors, thus opening the possibility of band gap engineering for this class of two-dimensional materials.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
By means of ab initio calculations, we investigate the possibility of existence of a boron nitride (BN) porous two-dimensional nanosheet, which is geometrically similar to the carbon allotrope known as biphenylene carbon. The proposed structure, which we called inorganic graphenylene (IGP), is formed spontaneously after selective dehydrogenation of the porous boron nitride (BN) structure proposed by Ding et al. We study the structural and electronic properties of both porous BN and IGP, and it is shown that, by selective substitution of B and N atoms with carbon atoms in these structures, the band gap can be significantly reduced, changing their behavior from insulators to semiconductors, thus opening the possibility of band gap engineering for this class of two-dimensional materials.
9.
E. Perim T. Botari, P. A. S. Autreto
Mechanical properties and fracture dynamics of silicene membranes Journal Article
Em: Phys. Chem. Chem. Phys., vol. 16, pp. 19417–19423, 2014.
@article{t2014mechanical,
title = {Mechanical properties and fracture dynamics of silicene membranes},
author = {T. Botari, E. Perim, P. A. S. Autreto, A. C. T. van Duin, R. Paupitz, D. S. Galvao},
url = {http://pubs.rsc.org/en/Content/ArticleLanding/2014/CP/C4CP02902J#!divAbstract},
year = {2014},
date = {2014-01-01},
journal = {Phys. Chem. Chem. Phys.},
volume = {16},
pages = {19417--19423},
abstract = {As graphene has become one of the most important materials, there is renewed interest in other similar structures. One example is silicene, the silicon analogue of graphene. It shares some of the remarkable graphene properties, such as the Dirac cone, but presents some distinct ones, such as a pronounced structural buckling. We have investigated, through density functional based tight-binding (DFTB), as well as reactive molecular dynamics (using ReaxFF), the mechanical properties of suspended single-layer silicene. We calculated the elastic constants, analyzed the fracture patterns and edge reconstructions. We also addressed the stress distributions, unbuckling mechanisms and the fracture dependence on the temperature. We analysed the differences due to distinct edge morphologies, namely zigzag and armchair.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
As graphene has become one of the most important materials, there is renewed interest in other similar structures. One example is silicene, the silicon analogue of graphene. It shares some of the remarkable graphene properties, such as the Dirac cone, but presents some distinct ones, such as a pronounced structural buckling. We have investigated, through density functional based tight-binding (DFTB), as well as reactive molecular dynamics (using ReaxFF), the mechanical properties of suspended single-layer silicene. We calculated the elastic constants, analyzed the fracture patterns and edge reconstructions. We also addressed the stress distributions, unbuckling mechanisms and the fracture dependence on the temperature. We analysed the differences due to distinct edge morphologies, namely zigzag and armchair.
10.
da Silva Autreto, Pedro Alves; Galvao, Douglas S; Artacho, Emilio
Species fractionation in atomic chains from mechanically stretched alloys Journal Article
Em: Journal of Physics: Condensed Matter, vol. 26, não 43, pp. 435304, 2014.
@article{da2014species,
title = {Species fractionation in atomic chains from mechanically stretched alloys},
author = {da Silva Autreto, Pedro Alves and Galvao, Douglas S and Artacho, Emilio},
url = {http://iopscience.iop.org/0953-8984/26/43/435304},
year = {2014},
date = {2014-01-01},
journal = {Journal of Physics: Condensed Matter},
volume = {26},
number = {43},
pages = {435304},
publisher = {IOP Publishing},
abstract = {Bettini et al (2006 Nat. Nanotechnol. 1 182–5) reported the first experimental realization of linear atomic chains (LACs) composed of different atoms (Au and Ag). The different contents of Au and Ag were observed in the chains from what was found in the bulk alloys, which raises the question of what the wire composition is, if it is in equilibrium with a bulk alloy. In this work we address the thermodynamic driving force for species fractionation in LACs under tension, and we present the density-functional theory results for Ag–Au chain alloys. A pronounced stabilization of the wires with an alternating Ag–Au sequence is observed, which could be behind the experimentally observed Au enrichment in LACs from alloys with high Ag content.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Bettini et al (2006 Nat. Nanotechnol. 1 182–5) reported the first experimental realization of linear atomic chains (LACs) composed of different atoms (Au and Ag). The different contents of Au and Ag were observed in the chains from what was found in the bulk alloys, which raises the question of what the wire composition is, if it is in equilibrium with a bulk alloy. In this work we address the thermodynamic driving force for species fractionation in LACs under tension, and we present the density-functional theory results for Ag–Au chain alloys. A pronounced stabilization of the wires with an alternating Ag–Au sequence is observed, which could be behind the experimentally observed Au enrichment in LACs from alloys with high Ag content.
11.
Paupitz, R; Autreto, Pedro AS; Legoas, SB; Srinivasan, S Goverapet; van Duin, Adri CT; Galvao, DS
Graphene to fluorographene and fluorographane: a theoretical study Journal Article
Em: Nanotechnology, vol. 24, não 3, pp. 035706, 2013.
@article{Paupitz2013,
title = {Graphene to fluorographene and fluorographane: a theoretical study},
author = {Paupitz, R and Autreto, Pedro AS and Legoas, SB and Srinivasan, S Goverapet and van Duin, Adri CT and Galvao, DS},
url = {http://iopscience.iop.org/0957-4484/24/3/035706/article?fromSearchPage=true},
year = {2013},
date = {2013-01-01},
journal = {Nanotechnology},
volume = {24},
number = {3},
pages = {035706},
publisher = {IOP Publishing},
abstract = {We report here a fully reactive molecular dynamics study on the structural and dynamical aspects of the fluorination of graphene membranes (fluorographene). Our results show that fluorination tends to produce defective areas on the graphene membranes with significant distortions of carbon–carbon bonds. Depending on the amount of incorporated fluorine atoms, large membrane holes were observed due to carbon atom losses. These results may explain the broad distribution of the structural lattice parameter values experimentally observed. We have also investigated the effects of mixing hydrogen and fluorine atoms on the graphene functionalization. Our results show that, when in small amounts, the presence of hydrogen atoms produces a significant decrease in the rate of fluorine incorporation onto the membrane. On the other hand, when fluorine is the minority element, it produces a significant catalytic effect on the rate of hydrogen incorporation. We have also observed the spontaneous formation of new hybrid structures with different stable configurations (chair-like, zigzag-like and boat-like) which we named fluorographane.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report here a fully reactive molecular dynamics study on the structural and dynamical aspects of the fluorination of graphene membranes (fluorographene). Our results show that fluorination tends to produce defective areas on the graphene membranes with significant distortions of carbon–carbon bonds. Depending on the amount of incorporated fluorine atoms, large membrane holes were observed due to carbon atom losses. These results may explain the broad distribution of the structural lattice parameter values experimentally observed. We have also investigated the effects of mixing hydrogen and fluorine atoms on the graphene functionalization. Our results show that, when in small amounts, the presence of hydrogen atoms produces a significant decrease in the rate of fluorine incorporation onto the membrane. On the other hand, when fluorine is the minority element, it produces a significant catalytic effect on the rate of hydrogen incorporation. We have also observed the spontaneous formation of new hybrid structures with different stable configurations (chair-like, zigzag-like and boat-like) which we named fluorographane.
12.
Perim, Eric; Santos, Ricardo Paupitz; Autreto, Pedro Alves da Silva; Galvao, Douglas S
Fracture Patterns of Boron Nitride Nanotubes Journal Article
Em: MRS Proceedings, vol. 1526, pp. mrsf12–1526, 2013.
@article{Perim2013,
title = {Fracture Patterns of Boron Nitride Nanotubes},
author = {Perim, Eric and Santos, Ricardo Paupitz and Autreto, Pedro Alves da Silva and Galvao, Douglas S},
year = {2013},
date = {2013-01-01},
journal = {MRS Proceedings},
volume = {1526},
pages = {mrsf12--1526},
publisher = {Cambridge University Press},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
13.
Autreto, PA; de Sousa, JM; Galvao, DS
On the Dynamics of Graphdiyne Hydrogenation Journal Article
Em: MRS Proceedings, vol. 1549, pp. 59–64, 2013.
@article{Autreto2013,
title = {On the Dynamics of Graphdiyne Hydrogenation},
author = {Autreto, PA and de Sousa, JM and Galvao, DS},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8915680&fileId=S1946427413006088},
year = {2013},
date = {2013-01-01},
journal = {MRS Proceedings},
volume = {1549},
pages = {59--64},
publisher = {Cambridge University Press},
abstract = {Graphene is a two-dimensional (2D) hexagonal array of carbon atoms in sp2-hybridized states. Graphene presents unique and exceptional electronic, thermal and mechanical properties. However, in its pristine state graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Because of this there is a renewed interest in other possible two-dimensional carbon-based structures similar to graphene. Examples of this are graphynes and graphdiynes, which are two-dimensional structures, composed of carbon atoms in sp2 and sp-hybridized states. Graphdiynes (benzenoid rings connecting two acetylenic groups) were recently synthesized and they can be intrinsically nonzero gap systems. These systems can be easily hydrogenated and the amount of hydrogenation can be used to tune the band gap value. In this work we have investigated, through fully atomistic molecular dynamics simulations with reactive force field (ReaxFF), the structural and dynamics aspects of the hydrogenation mechanisms of graphdiyne membranes. Our results showed that depending on whether the atoms are in the benzenoid rings or as part of the acetylenic groups, the rates of hydrogenation are quite distinct and change in time in a very complex pattern. Initially, the most probable sites to be hydrogenated are the carbon atoms forming the triple bonds, as expected. But as the amount of hydrogenation increases in time this changes and then the carbon atoms forming single bonds become the preferential sites. The formation of correlated domains observed in hydrogenated graphene is no longer observed in the case of graphdiynes. We have also carried out ab initio DFT calculations for model structures in order to test the reliability of ReaxFF calculations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphene is a two-dimensional (2D) hexagonal array of carbon atoms in sp2-hybridized states. Graphene presents unique and exceptional electronic, thermal and mechanical properties. However, in its pristine state graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Because of this there is a renewed interest in other possible two-dimensional carbon-based structures similar to graphene. Examples of this are graphynes and graphdiynes, which are two-dimensional structures, composed of carbon atoms in sp2 and sp-hybridized states. Graphdiynes (benzenoid rings connecting two acetylenic groups) were recently synthesized and they can be intrinsically nonzero gap systems. These systems can be easily hydrogenated and the amount of hydrogenation can be used to tune the band gap value. In this work we have investigated, through fully atomistic molecular dynamics simulations with reactive force field (ReaxFF), the structural and dynamics aspects of the hydrogenation mechanisms of graphdiyne membranes. Our results showed that depending on whether the atoms are in the benzenoid rings or as part of the acetylenic groups, the rates of hydrogenation are quite distinct and change in time in a very complex pattern. Initially, the most probable sites to be hydrogenated are the carbon atoms forming the triple bonds, as expected. But as the amount of hydrogenation increases in time this changes and then the carbon atoms forming single bonds become the preferential sites. The formation of correlated domains observed in hydrogenated graphene is no longer observed in the case of graphdiynes. We have also carried out ab initio DFT calculations for model structures in order to test the reliability of ReaxFF calculations.
14.
Perim, Eric; Paupitz, Ricardo; Autreto, PAS; Galvao, DS
The Hydrogenation Dynamics of h-BN Sheets Journal Article
Em: MRS Proceedings, vol. 1549, pp. 91–98, 2013.
@article{perim2013hydrogenation,
title = {The Hydrogenation Dynamics of h-BN Sheets},
author = {Perim, Eric and Paupitz, Ricardo and Autreto, PAS and Galvao, DS},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8943477&fileId=S1946427413007938},
year = {2013},
date = {2013-01-01},
journal = {MRS Proceedings},
volume = {1549},
pages = {91--98},
publisher = {Cambridge University Press},
abstract = {Hexagonal boron nitride (h-BN), also known as white graphite, is the inorganic analogue of graphite. Single layers of both structures have been already experimentally realized.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of hydrogenation of h-BN single-layers membranes.
Our results show that the rate of hydrogenation atoms bonded to the membrane is highly dependent on the temperature and that only at low temperatures there is a preferential bond to boron atoms. Unlike graphanes (hydrogenated graphene), hydrogenated h-BN membranes do not exhibit the formation of correlated domains. Also, the out-of-plane deformations are more pronounced in comparison with the graphene case. After a critical number of incorporated hydrogen atoms the membrane become increasingly defective, lost its two-dimensional character and collapses. The hydrogen radial pair distribution and second-nearest neighbor correlations were also analyzed.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hexagonal boron nitride (h-BN), also known as white graphite, is the inorganic analogue of graphite. Single layers of both structures have been already experimentally realized.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of hydrogenation of h-BN single-layers membranes.
Our results show that the rate of hydrogenation atoms bonded to the membrane is highly dependent on the temperature and that only at low temperatures there is a preferential bond to boron atoms. Unlike graphanes (hydrogenated graphene), hydrogenated h-BN membranes do not exhibit the formation of correlated domains. Also, the out-of-plane deformations are more pronounced in comparison with the graphene case. After a critical number of incorporated hydrogen atoms the membrane become increasingly defective, lost its two-dimensional character and collapses. The hydrogen radial pair distribution and second-nearest neighbor correlations were also analyzed.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of hydrogenation of h-BN single-layers membranes.
Our results show that the rate of hydrogenation atoms bonded to the membrane is highly dependent on the temperature and that only at low temperatures there is a preferential bond to boron atoms. Unlike graphanes (hydrogenated graphene), hydrogenated h-BN membranes do not exhibit the formation of correlated domains. Also, the out-of-plane deformations are more pronounced in comparison with the graphene case. After a critical number of incorporated hydrogen atoms the membrane become increasingly defective, lost its two-dimensional character and collapses. The hydrogen radial pair distribution and second-nearest neighbor correlations were also analyzed.
15.
Machado, LD; Autreto, PAS; Galvao, DS
Graphyne Oxidation: Insights From a Reactive Molecular Dynamics Investigation Journal Article
Em: MRS Proceedings, vol. 1549, pp. 53–58, 2013.
@article{Machado2013,
title = {Graphyne Oxidation: Insights From a Reactive Molecular Dynamics Investigation},
author = {Machado, LD and Autreto, PAS and Galvao, DS},
url = {http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8963025&fileId=S194642741300941X},
year = {2013},
date = {2013-01-01},
journal = {MRS Proceedings},
volume = {1549},
pages = {53--58},
publisher = {Cambridge University Press},
abstract = {Graphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Graphyne is a generic name for a family of carbon allotrope two-dimensional structures where sp2 (single and double bonds) and sp (triple bonds) hybridized states coexists. They exhibit very interesting electronic and mechanical properties sharing some of the unique graphene characteristics. Similarly to graphene, the graphyne electronic properties can be modified by chemical functionalization, such as; hydrogenation, fluorination and oxidation. Oxidation is of particular interest since it can produce significant structural damages.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.
In this work we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics and structural changes of the oxidation of single-layer graphyne membranes at room temperature. We have considered α, β, and γ-graphyne structures. Our results showed that the oxidation reactions are strongly site dependent and that the sp-hybridized carbon atoms are the preferential sites to chemical attacks. Our results also showed that the effectiveness of the oxidation (estimated from the number of oxygen atoms covalently bonded to carbon atoms) follows the α, β, γ-graphyne structure ordering. These differences can be explained by the fact that for α-graphyne structures the oxidation reactions occur in two steps: first, the oxygen atoms are trapped at the center of the large polygonal rings and then they react with the carbon atoms composing of the triple bonds. The small rings of γ-graphyne structures prevent these reactions to occur. The effectiveness of β-graphyne oxidation is between the α- and γ-graphynes.
16.
Perim, E; Autreto, PAS; Paupitz, R; Galvao, DS
Dynamical aspects of the unzipping of multiwalled boron nitride nanotubes Journal Article
Em: Physical Chemistry Chemical Physics, vol. 15, não 44, pp. 19147–19150, 2013.
@article{perim2013dynamical,
title = {Dynamical aspects of the unzipping of multiwalled boron nitride nanotubes},
author = {Perim, E and Autreto, PAS and Paupitz, R and Galvao, DS},
year = {2013},
date = {2013-01-01},
journal = {Physical Chemistry Chemical Physics},
volume = {15},
number = {44},
pages = {19147--19150},
publisher = {Royal Society of Chemistry},
abstract = {Boron nitride nanoribbons (BNNRs) exhibit very interesting magnetic properties, which could be very useful in the development of spintronic based devices. One possible route to obtain BNNRs is through the unzipping of boron nitride nanotubes (BNNTs), which have been already experimentally realized. In this work, different aspects of the unzipping process of BNNTs were investigated through fully atomistic molecular dynamics simulations using a classical reactive force field (ReaxFF). We investigated multiwalled BNNTs of different diameters and chiralities. Our results show that chirality plays a very important role in the unzipping process, as well as the interlayer coupling. These combined aspects significantly change the fracturing patterns and several other features of the unzipping processes in comparison to the ones observed for carbon nanotubes. Also, similar to carbon nanotubes, defective BNNTs can create regions of very high curvature which can act as a path to the unzipping process.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Boron nitride nanoribbons (BNNRs) exhibit very interesting magnetic properties, which could be very useful in the development of spintronic based devices. One possible route to obtain BNNRs is through the unzipping of boron nitride nanotubes (BNNTs), which have been already experimentally realized. In this work, different aspects of the unzipping process of BNNTs were investigated through fully atomistic molecular dynamics simulations using a classical reactive force field (ReaxFF). We investigated multiwalled BNNTs of different diameters and chiralities. Our results show that chirality plays a very important role in the unzipping process, as well as the interlayer coupling. These combined aspects significantly change the fracturing patterns and several other features of the unzipping processes in comparison to the ones observed for carbon nanotubes. Also, similar to carbon nanotubes, defective BNNTs can create regions of very high curvature which can act as a path to the unzipping process.
17.
Autreto, Pedro Alves da Silva; Galvao, Douglas S; Artacho, Emilio
Species Fractionation in Atomic Chains from Mechanically Stretched Alloys Journal Article
Em: arXiv preprint arXiv:1312.1285, 2013.
@article{autreto2013species,
title = {Species Fractionation in Atomic Chains from Mechanically Stretched Alloys},
author = {Autreto, Pedro Alves da Silva and Galvao, Douglas S and Artacho, Emilio},
year = {2013},
date = {2013-01-01},
journal = {arXiv preprint arXiv:1312.1285},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
18.
Gao, Guanhui; Mathkar, Akshay; Martins, Eric Perim; Galv ao, Douglas S; Gao, Duyang; da Silva Autreto, Pedro Alves; Sun, Chengjun; Cai, Lintao; Ajayan, Pulickel M; others,
Novel one--step synthesis of silver nanoparticles on hexagonal boron nitride nanosheets with antibacterial effect Journal Article
Em: 2013.
@article{gao2013novel,
title = {Novel one--step synthesis of silver nanoparticles on hexagonal boron nitride nanosheets with antibacterial effect},
author = {Gao, Guanhui and Mathkar, Akshay and Martins, Eric Perim and Galv~ao, Douglas S and Gao, Duyang and da Silva Autreto, Pedro Alves and Sun, Chengjun and Cai, Lintao and Ajayan, Pulickel M and others},
year = {2013},
date = {2013-01-01},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
19.
Maureen J Lagos Pedro A Autreto, Daniel Ugarte
Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts Conferência
Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts, não D1.3, MRSSpring 2012, 2012.
@conference{2012MRSSpring-D,
title = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
author = {Pedro A Autreto, Maureen J Lagos, Daniel Ugarte, Douglas S Galvao.},
url = {http://www.mrs.org/s12-program-d/
https://sites.ifi.unicamp.br/autretos/files/2015/04/2012MRSSpringMeeting-D-Program-Symposium-D-Nanocontacts–Emerging-Materials-and-Processing-for-Ohmicity-and-Rectification-2012-MRS-Spring-Meeting.pdf},
year = {2012},
date = {2012-04-10},
booktitle = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
number = {D1.3},
publisher = {MRSSpring 2012},
abstract = {The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).
20.
Autreto, Pedro A
Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts Apresentação
10.04.2012, (Work with Maureen J Lagos, Daniel Ugarte, Douglas S Galvao.).
@misc{2012MRSSpring-D-talking,
title = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
author = {Pedro A Autreto},
url = {http://www.mrs.org/s12-program-d/
https://sites.ifi.unicamp.br/autretos/files/2015/04/2012MRSSpringMeeting-D-Program-Symposium-D-Nanocontacts–Emerging-Materials-and-Processing-for-Ohmicity-and-Rectification-2012-MRS-Spring-Meeting.pdf},
year = {2012},
date = {2012-04-10},
booktitle = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
number = {D1.3},
publisher = {MRSSpring 2012},
abstract = {The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).},
note = {Work with Maureen J Lagos, Daniel Ugarte, Douglas S Galvao.},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).
2012
3.
Maureen J Lagos Pedro A Autreto, Daniel Ugarte
Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts Conferência
Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts, não D1.3, MRSSpring 2012, 2012.
Resumo | Links | BibTeX | Tags: ab initio, conductance, molecular dynamics, nanowires
@conference{2012MRSSpring-D,
title = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
author = {Pedro A Autreto, Maureen J Lagos, Daniel Ugarte, Douglas S Galvao.},
url = {http://www.mrs.org/s12-program-d/
https://sites.ifi.unicamp.br/autretos/files/2015/04/2012MRSSpringMeeting-D-Program-Symposium-D-Nanocontacts–Emerging-Materials-and-Processing-for-Ohmicity-and-Rectification-2012-MRS-Spring-Meeting.pdf},
year = {2012},
date = {2012-04-10},
booktitle = {Correlation between Quantum Conductance and Atomic Arrangement of Silver Atomic-Size Nanocontacts},
number = {D1.3},
publisher = {MRSSpring 2012},
abstract = {The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).},
keywords = {ab initio, conductance, molecular dynamics, nanowires},
pubstate = {published},
tppubtype = {conference}
}
The intense work of the nanotechnology community has increased the capabilities of researchers to produce new materials at the nanometric scale. As a result, novel physical and chemical behaviors are frequently reported opening opportunities for creating new kind of devices. These new devices will require a precise knowledge of the physical properties of atomic-size contacts and nanowires (NW)/interconnects. The generation of these atomic-size metal wires by the mechanical stretching has allowed the study of a wide range of metals at nanoscale. Due to the dominant role of surface energy in this size regime, several anomalous wire structures have already been reported to form during the stretching of very tiny wires, as hollow tubular metals and the size-limit to the existence of defects in NWs [1-3]. In this work we have studied the relevance of thermal effects on the structural and transport response of Ag atomic-size nanowires generated by mechanical elongation. Our study involve time-resolved atomic resolution transmission electron microscopy imaging and quantum conductance measurement using a ultra-high-vacuum mechanically he controllable break junction in association with quantum transport calculations. We have observed drastic changes in conductance and structural properties of Ag nanowires generated at different temperatures (150 and 300 K). By combining electron microscopy images, electronic transport measurements and theoretical modeling we have been able to establish a consistent correlation between the conductance and structural properties of Ag NWs. In particular, our study has revealed the formation of metastable rectangular rod-like Ag wire (3/3) along [001] direction. [1] M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. S. Galvao and D. Ugarte, Nature Nanotechnology v4, 149 (2009) [2] P. A. S. Autreto, M. J. Lagos, F. Sato, J. Bettini, V. Rodrigues, D. Ugarte, and D. S. Galvao, Phys. Rev. Lett. v106, 065501 (2011). [3] M. J. Lagos, F. Sato, D. S. Galvão, and D. Ugarte, Phys. Rev. Lett. v106, 055501 (2011).
2.
Pedro A Autreto Ricardo P dos Santos, Eric Perim
On the Unzipping Mechanisms of Carbon Nanotubes: Insights from Reactive Molecular Dynamics Simulations Conferência
On the Unzipping Mechanisms of Carbon Nanotubes: Insights from Reactive Molecular Dynamics Simulations, não DD1.4, MRSSpring 2012, 2012.
Resumo | Links | BibTeX | Tags: carbon nanotubes, mechanical properties, molecular dynamics, reaxFF
@conference{2012MRSSpring-DD,
title = {On the Unzipping Mechanisms of Carbon Nanotubes: Insights from Reactive Molecular Dynamics Simulations},
author = {Ricardo P dos Santos, Pedro A Autreto, Eric Perim, Gustavo Brunetto, Douglas S Galvao},
url = {http://www.mrs.org/s12-program-dd/
https://sites.ifi.unicamp.br/autretos/files/2015/04/2012MRSSpringMeeting-DD-Program-Symposium-D-Nanocontacts–Emerging-Materials-and-Processing-for-Ohmicity-and-Rectification-2012-MRS-Spring-Meeting.pdf},
year = {2012},
date = {2012-04-09},
booktitle = {On the Unzipping Mechanisms of Carbon Nanotubes: Insights from Reactive Molecular Dynamics Simulations},
number = {DD1.4},
publisher = {MRSSpring 2012},
abstract = {Graphene has been one of the hottest topics in materials science today. Due to its unique and unusual electronic properties graphene is been considered one of the most promising materials for the basis of a new nanoelectronics. However, in its pristine form graphene is a zero-gap semiconductor. This poses serious limitations to its use in some kind of electronic applications (some kind of transistors). In order to create non-zero graphene-like structures many approaches have been tried, such as, hydrogenation, fluorination and/or other chemical and physical functionalizations, with limited success. It has also been shown that making thin graphene stripes, the so-called graphene nanoribbons (GNRs), it is possible to create non-zero structures with some control of the process. But large scale and controlled GNR synthesis has been proved to be very difficult. Another possibility of producing GNR in a more controllable way is through cutting (unzipping) carbon nanotubes (CNTs). This has been achieved with different chemical [1] and physical [2] approaches. However, in spite of many experimental and theoretical studies on this problem, some important aspects remain to be fully understood. In this work we investigated the process of CNT fracture (unzipping) through molecular dynamics simulations using reactive force fields (ReaxFF), as implemented in the LAMMPS code. We considered multi-walled CNTs of different dimensions and chiralities and under mechanical stretching. Our results show that the unzipping mechanisms are highly dependent on CNT chirality. Well defined and distinct fracture patterns were observed for different chiralities. Zig-zag CNTs favor the creation of GNRs with well defined armchair edges, while armchair and chiral CNTs produde GNRs with less defined (defective) edges. The reasons why almost perfect linear CNT cuts are so frequently observed are also addressed. [1] D. V. Kosynkin et al., Nature v458, 872 (2009). [2] L. Jiao et al, Nature v458, 877 (2009).},
keywords = {carbon nanotubes, mechanical properties, molecular dynamics, reaxFF},
pubstate = {published},
tppubtype = {conference}
}
Graphene has been one of the hottest topics in materials science today. Due to its unique and unusual electronic properties graphene is been considered one of the most promising materials for the basis of a new nanoelectronics. However, in its pristine form graphene is a zero-gap semiconductor. This poses serious limitations to its use in some kind of electronic applications (some kind of transistors). In order to create non-zero graphene-like structures many approaches have been tried, such as, hydrogenation, fluorination and/or other chemical and physical functionalizations, with limited success. It has also been shown that making thin graphene stripes, the so-called graphene nanoribbons (GNRs), it is possible to create non-zero structures with some control of the process. But large scale and controlled GNR synthesis has been proved to be very difficult. Another possibility of producing GNR in a more controllable way is through cutting (unzipping) carbon nanotubes (CNTs). This has been achieved with different chemical [1] and physical [2] approaches. However, in spite of many experimental and theoretical studies on this problem, some important aspects remain to be fully understood. In this work we investigated the process of CNT fracture (unzipping) through molecular dynamics simulations using reactive force fields (ReaxFF), as implemented in the LAMMPS code. We considered multi-walled CNTs of different dimensions and chiralities and under mechanical stretching. Our results show that the unzipping mechanisms are highly dependent on CNT chirality. Well defined and distinct fracture patterns were observed for different chiralities. Zig-zag CNTs favor the creation of GNRs with well defined armchair edges, while armchair and chiral CNTs produde GNRs with less defined (defective) edges. The reasons why almost perfect linear CNT cuts are so frequently observed are also addressed. [1] D. V. Kosynkin et al., Nature v458, 872 (2009). [2] L. Jiao et al, Nature v458, 877 (2009).
2011
1.
Bruno I. Santos Gustavo Brunetto, Pedro A. Autreto; Galvao, Douglas S.
A Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene Conferência
A Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene, não AA15.102, MRS, 2011.
Resumo | Links | BibTeX | Tags: molecular dynamics, porous graphene
@conference{2011MRSFall,
title = {A Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene},
author = {Gustavo Brunetto, Bruno I. Santos, Pedro A. Autreto, Leonardo D. Machado, R. dos Santos and Douglas S. Galvao},
url = {http://www.mrs.org/f11-abstracts-aa/
https://sites.ifi.unicamp.br/autretos/files/2015/04/2011MRSFallMeeting-AA-Abstracts-Symposium-AA-Carbon-Nanotubes-Graphene-and-Related-Nanostructures..2011-MRS-Fall-Meeting.pdf},
year = {2011},
date = {2011-12-02},
booktitle = {A Nonzero Gap Two-Dimensional Carbon Allotrope from Porous Graphene},
number = {AA15.102},
publisher = {MRS},
abstract = {In the last decades many new carbon-based materials have been discovered. Examples of these materials are fullerenes, carbon nanotubes and graphene. Graphene has been one of the hottest topics in materials science in the last years. Graphene is a two dimensional array of hexagonal units of sp2 bonded carbon atoms with very unusual and interesting electronic and mechanical properties. Because of its special electronic properties, graphene is considered one of the most promising materials for future electronics. However, in its pristine state graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Many approaches have been tried to create, in a controlled way, a gap in graphene. Among these approaches we can mention oxidation and chemical functionalizations. Hydrogenated graphene-like structures have been recently synthesized, as the so-called porous graphene [1]. In this work we show, based on ab initio quantum molecular dynamics calculations, that porous graphene dehydrogenation can lead to a spontaneous formation of a nonzero gap two-dimensional carbon allotrope, called biphenylene carbon (BC). This structure presents the ideal properties to electronic applications. Besides exhibiting an intrinsic nonzero gap, BC also presents well delocalized frontier orbitals, suggestive of a structure with high electronic mobility. Possible synthetic routes to obtain BC are addressed. [1] Y. F. Li, Z. Zhou, P. W. Shen, and Z. F. Chen, Chem. Commun. v46, 3672 (2010).},
keywords = {molecular dynamics, porous graphene},
pubstate = {published},
tppubtype = {conference}
}
In the last decades many new carbon-based materials have been discovered. Examples of these materials are fullerenes, carbon nanotubes and graphene. Graphene has been one of the hottest topics in materials science in the last years. Graphene is a two dimensional array of hexagonal units of sp2 bonded carbon atoms with very unusual and interesting electronic and mechanical properties. Because of its special electronic properties, graphene is considered one of the most promising materials for future electronics. However, in its pristine state graphene is a gapless semiconductor, which poses some limitations to its use in some transistor electronics. Many approaches have been tried to create, in a controlled way, a gap in graphene. Among these approaches we can mention oxidation and chemical functionalizations. Hydrogenated graphene-like structures have been recently synthesized, as the so-called porous graphene [1]. In this work we show, based on ab initio quantum molecular dynamics calculations, that porous graphene dehydrogenation can lead to a spontaneous formation of a nonzero gap two-dimensional carbon allotrope, called biphenylene carbon (BC). This structure presents the ideal properties to electronic applications. Besides exhibiting an intrinsic nonzero gap, BC also presents well delocalized frontier orbitals, suggestive of a structure with high electronic mobility. Possible synthetic routes to obtain BC are addressed. [1] Y. F. Li, Z. Zhou, P. W. Shen, and Z. F. Chen, Chem. Commun. v46, 3672 (2010).
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