Pressure-induced Structural Phase Transition of Carbon Nanotubes into New Nanostructured Carbon Solids

2009 ◽  
Vol 1204 ◽  
Author(s):  
Masahiro Sakurai ◽  
Susumu Saito
Keyword(s):  
Phase Transition ◽  
Carbon Nanotubes ◽  
Molecular Dynamics ◽  
Structural Phase Transition ◽  
Density Functional ◽  
Local Density ◽  
Structural Phase ◽  
Tight Binding ◽  
Dynamics Simulation ◽  
Nanotube Bundles

AbstractWe study pressure-induced structural phase transition of carbon nanotubes using the constant-pressure tight-binding molecular-dynamics simulation. The systems studied are nanotube bundles composed of (6,6) armchair nanotube and/or (7,4) chiral nanotube, which are reported to be the nanotubes relatively abundant in experimentally purified sample. We find that the nanotube bundles transforms into a new phase that consist of graphitic ribbons and diamond blocks, “graphitic nanoribbon solid”. It is also found that sp3-rich phases obtained from the armchair nanotubes possess an anisotropic network and have high hardness which is comparable to that of cubic diamond. In the case of the bundles containing chiral nanotubes, on the other hand, amorphous diamond phase is obtained. Based on the local-density approximation in the density-functional theory, we also investigate the energetics and electronic structure of some of new carbon phases obtained in the molecular-dynamics study.

Structural Phase Transition from Fluorite to Orthorhombic FeSi2 by Tight Binding Molecular Dynamics

1995 ◽  
Vol 408 ◽  
Author(s):  
Leo Miglio ◽  
Massimo Celino ◽  
Valeria Meregalli ◽  
Francesca Tavazza
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Density Of States ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Tight Binding ◽  
Dynamics Simulation ◽  
Fluorite Phase ◽  
Electronic Density ◽  
Jahn Teller

AbstractIn this paper we report a molecular dynamics simulation at constant pressure and constant temperature of the structural phase transition occurring in epitaxial FeSi2 from the fluorite phase (metallic and pseudomorphic) to orthorhombic one (semiconductor and bulk stable). The evolution of the electronic density of states is carefully monitored during the transformation and we can show that the Jahn-Teller coupling between the density of states at the Fermi level and the lattice deformation drives the metal-semiconductor transition.

Quantum molecular dynamics simulation of Σ13 grain boundary in Si

1992 ◽  
Vol 50 (1) ◽  
pp. 212-213
Author(s):  
M.J. Kim ◽  
H. Ma ◽  
R.W. Carpenter ◽  
S.H. Lin ◽  
O.F. Sankey
Keyword(s):  
Molecular Dynamics ◽  
Grain Boundary ◽  
Density Functional ◽  
Local Density ◽  
Tight Binding ◽  
Equilibrium Structure ◽  
Dynamics Simulation ◽  
Boundary Structure ◽  
Quantum Molecular Dynamics ◽  
Binding Model

Grain boundary (GB) structure determination at an atomic level by HREM had received increasing attention in recent years. However, models of grain boundary structure deduced from the experiment results are usually not unique, and they do not necessarily represent the equilibrium structure. A newly developed quantum-molecular-dynamics (QMD) method, which does not depend on any empirical potentials, can be used to test these models and find the equilibrium atomic structure through simulated quenching. The method employs an electronic structure tight-binding model based on density functional theory within the local density approximation and the nonlocal pseudopotential scheme, and is used to compute the total energy and atomic forces for a variety of covalent materials. In the present study, this QMD method, coupled with image simulation, was used to predict the relaxed atomic configuration for the Σ=13 (510), [001] tilt grain boundary in Si.

Ab Initio Study of Structural Phase Transition and Electronic Properties in Samarium (Sm) Compounds

2016 ◽  
Vol 1141 ◽  
pp. 184-189
Author(s):  
Yeshvir Singh Panwar ◽  
Mahendra Aynyas ◽  
Jagdeesh Pataiya ◽  
Sankar P. Sanyal
Keyword(s):  
Phase Transition ◽  
Bulk Modulus ◽  
Structural Phase Transition ◽  
Local Density ◽  
Structural Phase ◽  
Tight Binding ◽  
Energy Band Diagram ◽  
Lattice Parameter ◽  
Type B ◽  
Lmto Method

The electronic structure and high pressure structural phase transition of SmTe and SmPo have been studied by using tight binding linear muffin-tin-orbital (TB-LMTO) method within the local density approximation (LDA). The total energy as a function of volume is obtained and it is found that these compounds are stable in NaCl-type (B1-phase) structure and transform to CsCl-type (B2-type) structure. The transition pressure of SmTe and SmPo are found to be 6.6 GPa and 8.6 GPa respectively. We have also calculated lattice parameter (a0), bulk modulus (B0), band structure (BS) and density of states (DOS). From energy band diagram, we observed that these compounds exhibit weakly metallic behaviour. The calculated values of lattice parameter and bulk modulus agree well with the available data.

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