http://scholar.google.com/citations?hl=en&user=95SvbM8AAAAJ
21.
Autreto, PAS; Legoas, SB; Flores, MZS; Galvao, DS
Carbon nanotube with square cross-section: An ab initio investigation Journal Article
Em: The Journal of chemical physics, vol. 133, não 12, pp. 124513, 2010.
@article{autreto2010carbon,
title = {Carbon nanotube with square cross-section: An ab initio investigation},
author = {Autreto, PAS and Legoas, SB and Flores, MZS and Galvao, DS},
url = {http://scitation.aip.org/content/aip/journal/jcp/133/12/10.1063/1.3483237},
year = {2010},
date = {2010-01-01},
journal = {The Journal of chemical physics},
volume = {133},
number = {12},
pages = {124513},
publisher = {AIP Publishing},
abstract = {Recently, Lagos et al. [Nat. Nanotechnol.4, 149 (2009)] reported the discovery of the smallest possible silver square cross-section nanotube. A natural question is whether similar carbon nanotubes can exist. In this work we report ab initio results for the structural, stability, and electronic properties for such hypothetical structures. Our results show that stable (or at least metastable) structures are possible with metallic properties. They also show that these structures can be obtained by a direct interconversion from SWNT(2,2). Large finite cubanelike oligomers, topologically related to these new tubes, were also investigated.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, Lagos et al. [Nat. Nanotechnol.4, 149 (2009)] reported the discovery of the smallest possible silver square cross-section nanotube. A natural question is whether similar carbon nanotubes can exist. In this work we report ab initio results for the structural, stability, and electronic properties for such hypothetical structures. Our results show that stable (or at least metastable) structures are possible with metallic properties. They also show that these structures can be obtained by a direct interconversion from SWNT(2,2). Large finite cubanelike oligomers, topologically related to these new tubes, were also investigated.
22.
Coluci, VR; Timoteo, VS; Galvao, DS
Thermophoretically driven carbon nanotube oscillators Journal Article
Em: Applied Physics Letters, vol. 95, não 25, pp. 253103, 2009.
@article{coluci2009thermophoretically,
title = {Thermophoretically driven carbon nanotube oscillators},
author = {Coluci, VR and Timoteo, VS and Galvao, DS},
url = {http://scitation.aip.org/content/aip/journal/apl/95/25/10.1063/1.3276546},
year = {2009},
date = {2009-01-01},
journal = {Applied Physics Letters},
volume = {95},
number = {25},
pages = {253103},
publisher = {AIP Publishing},
abstract = {The behavior of a nanodevice based upon double-walled carbon nanotubeoscillators driven by periodically applied thermal gradients (7 and 17 K/nm) is investigated by numerical calculations and classical molecular dynamics simulations. Our results indicate that thermophoresis can be effective to initiate the oscillator and that suitable heat pulses may provide an appropriate way to tune its behavior. Sustained regular oscillatory as well as chaotic motions were observed for the systems investigated in this work.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The behavior of a nanodevice based upon double-walled carbon nanotubeoscillators driven by periodically applied thermal gradients (7 and 17 K/nm) is investigated by numerical calculations and classical molecular dynamics simulations. Our results indicate that thermophoresis can be effective to initiate the oscillator and that suitable heat pulses may provide an appropriate way to tune its behavior. Sustained regular oscillatory as well as chaotic motions were observed for the systems investigated in this work.
23.
Nakabayashi, D; Ugarte, D; Moreau, ALD; Coluci, VR; Galvao, DS; Cotta, MA
Carbon nanotubes as R-bars of high aspect ratio composite nanotools Technical Report
2008.
@techreport{nakabayashi2008carbonb,
title = {Carbon nanotubes as R-bars of high aspect ratio composite nanotools},
author = {Nakabayashi, D and Ugarte, D and Moreau, ALD and Coluci, VR and Galvao, DS and Cotta, MA},
url = {http://lnls.cnpem.br/ar2008/},
year = {2008},
date = {2008-01-01},
abstract = {Nano technology requires the development of nano scale tools to manipulate nano systems. From the point of view of materials science, this represents a serious challenge, because nano tools must meet a series of stringent requirements of shape (size, aspect ratio), mechanical, magnetic and electrical properties. We have developed long and narrow carbon-carbon composite nano tips using carbon nanotubes covered by an amorphous carbon shell; the very small nano tube tip remained uncoated to preserve apex size. This configuration renders the system stiffer and allows for the control of flexibility and vibrations. In addition, we have maintained the important nano tube properties of size, strength and resilience. Nano manipulation experiments in situ in a high resolution scanning electron microscope were used to optimize the tips behavior and molecular dynamics simulations were used to study the mechanical response. Finally, we performed a practical application in atomic force microscopy. Composite tips yielded excellent image resolution and showed remarkable wear resistance (no degradation of image quality after acquiring several hundred images). },
keywords = {},
pubstate = {published},
tppubtype = {techreport}
}
Nano technology requires the development of nano scale tools to manipulate nano systems. From the point of view of materials science, this represents a serious challenge, because nano tools must meet a series of stringent requirements of shape (size, aspect ratio), mechanical, magnetic and electrical properties. We have developed long and narrow carbon-carbon composite nano tips using carbon nanotubes covered by an amorphous carbon shell; the very small nano tube tip remained uncoated to preserve apex size. This configuration renders the system stiffer and allows for the control of flexibility and vibrations. In addition, we have maintained the important nano tube properties of size, strength and resilience. Nano manipulation experiments in situ in a high resolution scanning electron microscope were used to optimize the tips behavior and molecular dynamics simulations were used to study the mechanical response. Finally, we performed a practical application in atomic force microscopy. Composite tips yielded excellent image resolution and showed remarkable wear resistance (no degradation of image quality after acquiring several hundred images).
24.
Nakabayashi, D; Moreau, ALD; Coluci, VR; Galvao, DS; Cotta, MA; Ugarte, D
Carbon nanotubes as reinforcement elements of composite nanotools Journal Article
Em: Nano letters, vol. 8, não 3, pp. 842–847, 2008.
@article{nakabayashi2008carbon,
title = {Carbon nanotubes as reinforcement elements of composite nanotools},
author = {Nakabayashi, D and Moreau, ALD and Coluci, VR and Galvao, DS and Cotta, MA and Ugarte, D},
url = {http://pubs.acs.org/doi/abs/10.1021/nl0729633},
year = {2008},
date = {2008-01-01},
journal = {Nano letters},
volume = {8},
number = {3},
pages = {842--847},
publisher = {American Chemical Society},
abstract = {Nanotechnology is stimulating the development of nanomanipulators, including tips to interact with individual nanosystems. Fabricating nanotips fulfilling the requirements of shape (size, aspect ratio), mechanical, magnetic, and electrical properties is a material science challenge. Here, we report the generation of reinforced carbon−carbon composite nanotools using a nanotube (CNTs) covered by an amorphous carbon matrix (shell); the CNT tip protruded and remained uncoated to preserve apex size. Unsuitable properties such as flexibility and vibration could be controlled without deteriorating the CNT size, strength, and resilience. Nanomanipulation experiments and molecular dynamics simulations have been used to study the mechanical response of these composite beams under bending efforts. AFM probes based on these C−C composite high aspect ratio tips generated excellent image resolution and showed no degradation after acquiring several hundred (400) images.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Nanotechnology is stimulating the development of nanomanipulators, including tips to interact with individual nanosystems. Fabricating nanotips fulfilling the requirements of shape (size, aspect ratio), mechanical, magnetic, and electrical properties is a material science challenge. Here, we report the generation of reinforced carbon−carbon composite nanotools using a nanotube (CNTs) covered by an amorphous carbon matrix (shell); the CNT tip protruded and remained uncoated to preserve apex size. Unsuitable properties such as flexibility and vibration could be controlled without deteriorating the CNT size, strength, and resilience. Nanomanipulation experiments and molecular dynamics simulations have been used to study the mechanical response of these composite beams under bending efforts. AFM probes based on these C−C composite high aspect ratio tips generated excellent image resolution and showed no degradation after acquiring several hundred (400) images.
25.
Coluci, Vitor R; Hall, Lee J; Kozlov, Mikhail E; Zhang, Mei; Dantas, Socrates O; Galvao, Douglas S; Baughman, Ray H
Modeling the auxetic transition for carbon nanotube sheets Journal Article
Em: Physical Review B, vol. 78, não 11, pp. 115408, 2008.
@article{coluci2008modeling,
title = {Modeling the auxetic transition for carbon nanotube sheets},
author = {Coluci, Vitor R and Hall, Lee J and Kozlov, Mikhail E and Zhang, Mei and Dantas, Socrates O and Galvao, Douglas S and Baughman, Ray H},
url = {http://journals.aps.org/prb/abstract/10.1103/PhysRevB.78.115408},
year = {2008},
date = {2008-01-01},
journal = {Physical Review B},
volume = {78},
number = {11},
pages = {115408},
publisher = {APS},
abstract = {A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A simple model is developed to predict the complex mechanical properties of carbon nanotube sheets (buckypaper) [L. J. Hall et al., Science 320, 504 (2008)]. Fabricated using a similar method to that deployed for making writing paper, these buckypapers can have in-plane Poisson’s ratios changed from positive to negative, becoming auxetic, as multiwalled carbon nanotubes are increasingly mixed with single-walled carbon nanotubes. Essential structural features of the buckypapers are incorporated into the model: isotropic in-plane mechanical properties, nanotubes preferentially oriented in the sheet plane, and freedom to undergo stress-induced elongation by both angle and length changes. The expressions derived for the Poisson’s ratios enabled quantitative prediction of both observed properties and remarkable new properties obtainable by structural modification.
26.
Braga, Scheila Furtado; Galvao, Douglas Soares
Molecular dynamics simulation of single wall carbon nanotubes polymerization under compression Journal Article
Em: Journal of Computational Chemistry, vol. 28, não 10, pp. 1724–1734, 2007.
@article{braga2007molecular,
title = {Molecular dynamics simulation of single wall carbon nanotubes polymerization under compression},
author = {Braga, Scheila Furtado and Galvao, Douglas Soares},
url = {http://onlinelibrary.wiley.com/store/10.1002/jcc.20684/asset/20684_ftp.pdf?v=1&t=i52l5iyb&s=94cda082eed01cd61890fffe50aad5e26cdda7d1},
year = {2007},
date = {2007-01-01},
journal = {Journal of Computational Chemistry},
volume = {28},
number = {10},
pages = {1724--1734},
publisher = {Wiley Subscription Services, Inc., A Wiley Company},
abstract = {Single wall carbon nanotubes (SWCNTs) often aggregate into bundles of hundreds of weakly interacting
tubes. Their cross-polymerization opens new possibilities for the creation of new super-hard materials. New mechanical
and electronic properties are expected from these condensed structures, as well as novel potential applications. Previous
theoretical results presented geometric modifications involving changes in the radial section of the compressed tubes
as the explanation to the experimental measurements of structural changes during tube compression. We report here
results from molecular dynamics simulations of the SWCNTs polymerization for small diameter arm chair tubes under
compression. Hydrostatic and piston-type compression of SWCNTs have been simulated for different temperatures and
rates of compression. Our results indicate that large diameter tubes (10,10) are unlike to polymerize while small diameter
ones (around 5 Å) polymerize even at room temperature. Other interesting results are the observation of the appearance
of spontaneous scroll-like structures and also the so-called tubulane motifs, which were predicted in the literature more
than a decade ago},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Single wall carbon nanotubes (SWCNTs) often aggregate into bundles of hundreds of weakly interacting
tubes. Their cross-polymerization opens new possibilities for the creation of new super-hard materials. New mechanical
and electronic properties are expected from these condensed structures, as well as novel potential applications. Previous
theoretical results presented geometric modifications involving changes in the radial section of the compressed tubes
as the explanation to the experimental measurements of structural changes during tube compression. We report here
results from molecular dynamics simulations of the SWCNTs polymerization for small diameter arm chair tubes under
compression. Hydrostatic and piston-type compression of SWCNTs have been simulated for different temperatures and
rates of compression. Our results indicate that large diameter tubes (10,10) are unlike to polymerize while small diameter
ones (around 5 Å) polymerize even at room temperature. Other interesting results are the observation of the appearance
of spontaneous scroll-like structures and also the so-called tubulane motifs, which were predicted in the literature more
than a decade ago
tubes. Their cross-polymerization opens new possibilities for the creation of new super-hard materials. New mechanical
and electronic properties are expected from these condensed structures, as well as novel potential applications. Previous
theoretical results presented geometric modifications involving changes in the radial section of the compressed tubes
as the explanation to the experimental measurements of structural changes during tube compression. We report here
results from molecular dynamics simulations of the SWCNTs polymerization for small diameter arm chair tubes under
compression. Hydrostatic and piston-type compression of SWCNTs have been simulated for different temperatures and
rates of compression. Our results indicate that large diameter tubes (10,10) are unlike to polymerize while small diameter
ones (around 5 Å) polymerize even at room temperature. Other interesting results are the observation of the appearance
of spontaneous scroll-like structures and also the so-called tubulane motifs, which were predicted in the literature more
than a decade ago
27.
Troche, KS; Coluci, VR; Rurali, R; Galvao, DS
Structural and electronic properties of zigzag carbon nanotubes filled with small fullerenes Journal Article
Em: Journal of Physics: Condensed Matter, vol. 19, não 23, pp. 236222, 2007.
@article{troche2007structural,
title = {Structural and electronic properties of zigzag carbon nanotubes filled with small fullerenes},
author = {Troche, KS and Coluci, VR and Rurali, R and Galvao, DS},
url = {http://iopscience.iop.org/0953-8984/19/23/236222},
year = {2007},
date = {2007-01-01},
journal = {Journal of Physics: Condensed Matter},
volume = {19},
number = {23},
pages = {236222},
publisher = {IOP Publishing},
abstract = {In this work we investigated the encapsulation of C20 and C30 fullerenes into semiconducting carbon nanotubes to study the possibility of bandgap engineering in such systems. Classical molecular dynamics simulations coupled to tight-binding calculations were used to determine the conformational and electronic properties of carbon nanotubes with an increasing fullerene concentration. We have observed that C20 fullerenes behave similarly to a n-type dopant while C30 can provide p-type doping in some cases. The combined incorporation of both types of fullerenes (hybrid encapsulation) into the same nanotube leads to a behaviour similar to that found in electronic pn-junctions. These aspects can be exploited in the design of nanoelectronic devices using semiconducting carbon nanotubes.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this work we investigated the encapsulation of C20 and C30 fullerenes into semiconducting carbon nanotubes to study the possibility of bandgap engineering in such systems. Classical molecular dynamics simulations coupled to tight-binding calculations were used to determine the conformational and electronic properties of carbon nanotubes with an increasing fullerene concentration. We have observed that C20 fullerenes behave similarly to a n-type dopant while C30 can provide p-type doping in some cases. The combined incorporation of both types of fullerenes (hybrid encapsulation) into the same nanotube leads to a behaviour similar to that found in electronic pn-junctions. These aspects can be exploited in the design of nanoelectronic devices using semiconducting carbon nanotubes.
28.
Braga, SF; Galvao, DS
Single wall carbon nanotubes polymerization under compression: An atomistic molecular dynamics study Journal Article
Em: Chemical physics letters, vol. 419, não 4, pp. 394–399, 2006.
@article{braga2006single,
title = {Single wall carbon nanotubes polymerization under compression: An atomistic molecular dynamics study},
author = {Braga, SF and Galvao, DS},
url = {http://www.sciencedirect.com/science/article/pii/S0009261405018592},
year = {2006},
date = {2006-01-01},
journal = {Chemical physics letters},
volume = {419},
number = {4},
pages = {394--399},
publisher = {Elsevier},
abstract = {Recently, it was reported experimental observations of crosslinking between carbon nanotubes (CNTs) under pressure. Similarly to CNT growth formation the details of these polymerization processes are still unclear. In this work, we report a molecular dynamics simulation of the polymerization of a bundle of single-wall carbon nanotubes under compression using Brenner reactive potentials. Our results show that for small tube diameters extensive crosslinking formation can occur. For larger tube diameter, we obtained the first theoretical evidences that scroll-like structures (recently experimentally obtained) can be formed from SWCNTs.
},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, it was reported experimental observations of crosslinking between carbon nanotubes (CNTs) under pressure. Similarly to CNT growth formation the details of these polymerization processes are still unclear. In this work, we report a molecular dynamics simulation of the polymerization of a bundle of single-wall carbon nanotubes under compression using Brenner reactive potentials. Our results show that for small tube diameters extensive crosslinking formation can occur. For larger tube diameter, we obtained the first theoretical evidences that scroll-like structures (recently experimentally obtained) can be formed from SWCNTs.
29.
Coluci, VR; Legoas, SB; de Aguiar, MAM; Galvao, DS
Chaotic signature in the motion of coupled carbon nanotube oscillators Journal Article
Em: Nanotechnology, vol. 16, não 4, pp. 583, 2005.
@article{coluci2005chaotic,
title = {Chaotic signature in the motion of coupled carbon nanotube oscillators},
author = {Coluci, VR and Legoas, SB and de Aguiar, MAM and Galvao, DS},
url = {http://iopscience.iop.org/0957-4484/16/4/041},
year = {2005},
date = {2005-01-01},
journal = {Nanotechnology},
volume = {16},
number = {4},
pages = {583},
publisher = {IOP Publishing},
abstract = {The motion of coupled oscillators based on multiwalled carbon nanotubes is studied using rigid-body dynamics simulations. The results show the existence of chaotic and regular behaviours for a given total energy, indicating the manifestation of chaos in nanoscaled mechanical systems based on carbon nanotube oscillators. Different regular motions are observed for different total energies, and they can be obtained by appropriately choosing the initial conditions. This possibility can allow the construction of multi-functional nano-devices based on multiwalled carbon nanotube oscillators.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The motion of coupled oscillators based on multiwalled carbon nanotubes is studied using rigid-body dynamics simulations. The results show the existence of chaotic and regular behaviours for a given total energy, indicating the manifestation of chaos in nanoscaled mechanical systems based on carbon nanotube oscillators. Different regular motions are observed for different total energies, and they can be obtained by appropriately choosing the initial conditions. This possibility can allow the construction of multi-functional nano-devices based on multiwalled carbon nanotube oscillators.
30.
Legoas, SB; Coluci, VR; Braga, SF; Coura, PZ; Dantas, SO; Galvao, DS
Gigahertz nanomechanical oscillators based on carbon nanotubes Journal Article
Em: Nanotechnology, vol. 15, não 4, pp. S184, 2004.
@article{legoas2004gigahertz,
title = {Gigahertz nanomechanical oscillators based on carbon nanotubes},
author = {Legoas, SB and Coluci, VR and Braga, SF and Coura, PZ and Dantas, SO and Galvao, DS},
url = {http://iopscience.iop.org/0957-4484/15/4/012},
year = {2004},
date = {2004-01-01},
journal = {Nanotechnology},
volume = {15},
number = {4},
pages = {S184},
publisher = {IOP Publishing},
abstract = {We report molecular dynamics studies of carbon nanotubes as mechanical gigahertz oscillators. Our results show that different oscillatory regimes exist but that sustained oscillations are possible only when the radii difference values of the inner and outer tubes are {sim }3.4~AA . Frequencies as large as 87 GHz were obtained. Calculated force and frequency values are in good agreement with estimated data from recent experimental investigations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report molecular dynamics studies of carbon nanotubes as mechanical gigahertz oscillators. Our results show that different oscillatory regimes exist but that sustained oscillations are possible only when the radii difference values of the inner and outer tubes are {\sim }3.4~\AA . Frequencies as large as 87 GHz were obtained. Calculated force and frequency values are in good agreement with estimated data from recent experimental investigations.
31.
VR Coluci SB Legoas, SF Braga
Molecular-dynamics simulations of carbon nanotubes as gigahertz oscillators Journal Article
Em: Physical Review Letters, vol. 90, não 5, pp. 055504, 2003.
@article{legoas2003molecularb,
title = {Molecular-dynamics simulations of carbon nanotubes as gigahertz oscillators},
author = {SB Legoas, VR Coluci, SF Braga, PZ Coura, SO Dantas, DS Galvao},
year = {2003},
date = {2003-01-01},
journal = {Physical Review Letters},
volume = {90},
number = {5},
pages = {055504},
abstract = {Recently, Zheng and Jiang [Phys. Rev. Lett. 88, 045503 (2002)] have proposed that multiwalled carbon nanotubes could be the basis for a new generation of nano-oscillators in the several gigahertz range. In this Letter, we present the first molecular dynamics simulation for these systems. Different nanotube types were considered in order to verify the reliability of such devices as gigahertz oscillators. Our results show that these nano-oscillators are dynamically stable when the radii difference values between inner and outer tubes are of ∼3.4 Å. Frequencies as large as 38 GHz were observed, and the calculated force values are in good agreement with recent experimental investigations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, Zheng and Jiang [Phys. Rev. Lett. 88, 045503 (2002)] have proposed that multiwalled carbon nanotubes could be the basis for a new generation of nano-oscillators in the several gigahertz range. In this Letter, we present the first molecular dynamics simulation for these systems. Different nanotube types were considered in order to verify the reliability of such devices as gigahertz oscillators. Our results show that these nano-oscillators are dynamically stable when the radii difference values between inner and outer tubes are of ∼3.4 Å. Frequencies as large as 38 GHz were observed, and the calculated force values are in good agreement with recent experimental investigations.
Desculpe, nenhuma publicação.
