Towards Multiscale Simulations of Carbon Nanotube Growth Process: A Density Functional Theory Study of Transition Metal Hydrides (original) (raw)
Related papers
Nano Research, 2009
We present a brief review of the most important efforts aimed at simulating single-walled carbon nanotube (SWNT) nucleation and growth processes using molecular dynamics (MD) techniques reported in the literature. MD simulations allow the spatio-temporal movement of atoms during nonequilibrium growth to be followed. Thus, it is hoped that a successful MD simulation of the entire SWNT formation process will assist in the design of chirality-specifi c SWNT synthesis techniques. We give special consideration to the role of the metal catalyst particles assumed in standard theories of SWNT formation, and describe the actual metal behavior observed in the reported MD simulations, including our own recent quantum chemical MD simulations. It is concluded that the use of a quantum potential is essential for a qualitatively correct description of the catalytic behavior of the metal cluster, and that carbide formation does not seem to be a necessary requirement for nucleation and growth of SWNTs according to our most recent quantum chemical MD simulations.
Large scale simulations for carbon nanotubes
Proceedings - Seventh International Conference on High Performance Computing and Grid in Asia Pacific Region, HPCAsia 2004, 2004
Nano carbon materials as nanotubes (CNTs) and fullerenes in nanotechnology have a lot of potential for industrial applications. On the efforts of developing applications, it has been recognized that computational simulations are powerful and efficient tools to find and create new materials from nano scale. Aiming at realistic simulations for nonmaterial, we have developed a large-scale computation technique utilizing tight binding molecular dynamic method, ab initio density functional theory (DFT), GSW rearrangement and time-dependent DFT method. We have studies various physical properties of nano-carbon and applications e.g., (1) Nano-structural deformation by ion irradiation, (2) Atomic and Electronic Structures of Contact between Carbon Nanotube and Titanium, (3) Generation of new atomic structure using GSW rearrangement, (4) Composite material formed from twisted CNTs, (5) Hole-doped diamond superconductor. In addition to nano carbon as nanotube, diamond and graphite of traditional carbon material came into limelight. Along these works, we have realized that the Earth Simulator is a very powerful tool for large-scale material simulations.
TechConnect Briefs, 2005
The rapid development of nanotechnology has created significant interest to predicting the behavior of materials from the atomic to the engineering scales. However, it was found that such a prediction is a very challenging problem because existing atomistic models are rather slow, while reactor-scale codes are not capable of capturing nanoscale effects. This paper addresses this problem by introducing a Multi Scale Computational Framework which couples a continuum model of reactor-scale processes, a Kinetic Monte Carlo (KMC) solver for the growth of molecular structures, and a Molecular Dynamics (MD) software for the self-assembly of atoms into molecular structures. Reactor-scale and atomistic KMC simulations were linked using a "Gap-tooth" algorithm, and KMC and MD were coupled by a "Coarse time-stepper" method.
Computational Studies of Small Carbon and Iron-Carbon Systems Relevant to Carbon Nanotube Growth
Journal of Nanoscience and Nanotechnology, 2008
Density functional theory (DFT) calculations show that dimers and longer carbon strings are more stable than individual atoms on Fe(111) surfaces. It is therefore necessary to consider the formation of these species on the metal surfaces and their effect on the mechanism of single-walled nanotube (SWNT) growth. The good agreement between the trends (energies and structures) obtained using DFT and those based on the Brenner and AIREBO models indicate that these analytic models provide adequate descriptions of the supported carbon systems needed for valid molecular dynamics simulations of SWNT growth. In contrast, the AIREBO model provides a better description of the relative energies for isolated carbon species, and this model is preferred over the Brenner potential when simulating SWNT growth in the absence of metal particles. However, the PM3 semiempirical model appears to provide an even better description for these systems and, given sufficient computer resources, direct dynamics methods based on this model may be preferred.
Physical review. B, Condensed matter
The O(N) and parallelization techniques have been successfully applied in tight-binding molecular-dynamics simulations of single-walled carbon nanotubes (SWNTs) of various chiralities. The accuracy of the O(N) description is found to be enhanced by the use of basis functions of neighboring atoms (buffer). The importance of buffer size in evaluating the simulation time, total energy, and force values together with electronic temperature has been shown. Finally, through the local density of state results, the metallic and semiconducting behavior of (10x10) armchair and (17x0) zigzag SWNT s, respectively, has been demonstrated. Comment: 15 pages, 10 figures
Multi-Scale Modeling of Processing of Carbon Nanotubes
2005
As technologies are continuously advancing, new semiconductor materials and novel devices are being developed which are indispensable for electronic applications. Progress in the computer aided design of fabrication of nanoscale materials lags behind experimental advances, since atomistic simulation methods are computationally impractical, while mesoscopic simulation methods are not capable of capturing nanoscale effects. Multi-Scale Computational Framework is introduced to conduct over 3 scales, continuum model of reactor-scale processes, kinetic Monte Carlo for the growth of nanostructures, and molecular dynamics for the prediction of reaction rates. “Gap-tooth” algorithm and “coarse timestepper” method are employed to couple the scales. The results of multiscale simulation for growth of carbon nanotubes by plasma enhanced chemical vapor deposition are presented.
Nano Research, 2009
Density functional theory (DFT) and tight binding (TB) models have been used to study systems containing single-walled carbon nanotubes (SWNTs) and metal clusters that are of relevance to SWNT growth and regrowth. In particular, TB-based Monte Carlo (TBMC) simulations at 1000 or 1500 K show that Ni atoms that are initially on the surface of the SWNT or that are clustered near the SWNT end diffuse to the nanotube end so that virtually none of the Ni atoms are located inside the nanotube. This occurs, in part, due to the lowering of the Ni atom energies when they retract from the SWNT to the interior of the cluster. Aggregation of the atoms at the SWNT end does not change the chirality within the simulation time, which supports the application of SWNT regrowth (seeded growth) as a potential route for chirality-controlled SWNT production. DFT-based geometry optimisation and direct dynamics at 2000 K show that Cr and Mo atoms in Cr 5 Co 50 and Mo 5 Co 50 clusters prefer to be distributed in the interior of the clusters. Extension of these calculations should deepen our understanding of the role of the various alloy components in SWNT growth.