Highlights

Three types of simulations developed by GSONMers have been highlighted in three of most important magazines in Material Sciences.

Dynamical aspects of the unzipping of multiwalled boron nitride nanotube

E. PerimaP. A. S. AutretoaR. Paupitz*b and D. S. Galvaoa
aInstituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, 13083-970, Campinas, São Paulo, Brazil
bDepartamento de Física, IGCE, Universidade Estadual Paulista, UNESP, 13506-900, Rio Claro, SP, Brazil.

 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.

Simulating Pump–Probe Photoelectron and Absorption Spectroscopy on the Attosecond Timescale with Time-Dependent Density Functional Theory

  Dr. U. De Giovannini, G. Brunetto, J. Walkenhorst, Prof. Dr. A. Rubio Nano-Bio Spectroscopy Group and ETSF Scientific Development Center University of the Basque Country UPV/EHU
Avenida de Tolosa 72, 20018 San Sebastian (Spain)
Prof. Dr. A. Rubio
Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC Av. Tolosa 72, 20018 San Sebastiμn (Spain)
and
Fritz-Haber-Institut der Max-Planck-Gesellschaft
Faradayweg 4-6, 14195 Berlin (Germany)
Dr. A. Castro
ARAID Foundation - Institute for Biocomputation
and Physics of Complex Systems, University of Zaragoza Mariano Esquillor Gómez s/n, 50018 Zaragoza, (Spain)
G. Brunetto
Instituto de Física “Gleb Wataghin” Universidade Estadual de Campinas 13083-970, Campinas, S1⁄4o Paulo (Brazil)

Molecular absorption and photoelectron spectra can be efficiently predicted with real-time time-dependent density functional theory. We show herein how these techniques can be easily extended to study time-resolved pump–probe experiments, in which a system response (absorption or electron emission) to a probe pulse is measured in an excited state. This simulation tool helps with the interpretation of fast-evolving attosecond time-resolved spectroscopic experiments, in which electronic motion must be followed at its natural timescale. We show how the extra degrees of freedom (pump-pulse duration, intensity, frequency, and time delay), which are absent in a conventional steady-state experiment, provide additional information about electronic structure and dynamics that improve characterization of a system. As an extension of this approach, time-dependent 2D spectroscopy can also be simulated, in principle, for large-scale structures and extended systems.

Dynamics of the Formation of Carbon Nanotube Serpentines

L. D. Machado1, S. B. Legoas2, J. S. Soares3, N. Shadmi4, A. Jorio3, E. Joselevich4, and D. S. Galvão1
1Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, C. P. 6165, 13083-970 Campinas, Sao Paulo, Brazil
2Departamento de Física, CCT, Universidade Federal de Roraima, 69304-000 Boa Vista, Roraima, Brazil
3Departamento de Física, Universidade Federal de Minas Gerais, 30123-970 Belo Horizonte, Minas Gerais, Brazil
4Department of Materials and Interfaces, Weizmann Institute of Science, Rehovot 76100, Israel

 

Recently, Geblinger et al. [Nat. Nanotechnol. 3, 195 (2008)] reported the experimental realization of carbon nanotube    -like shaped nanostructures, the so-called carbon nanotube serpentines. We report here results from multimillion fully atomistic molecular dynamics simulations of their formation. We consider one- μm  -long carbon nanotubes placed on stepped substrates with and without a catalyst nanoparticle on the top free end of the tube. A force is applied to the upper part of the tube during a short period of time and turned off; then the system is set free to evolve in time. Our results show that these conditions are sufficient to form robust serpentines and validates the general features of the “falling spaghetti model” proposed to explain their formation.