Large Scale Molecular Dynamics Study of Amorphous Carbon and Graphite on Parallel Machines
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ANDREY OMELTCHENKO,
RAJIV K. KALIA,
PRIYA VASHISHTA
Concurrent Computing Laboratory for Materials Simulations Department of Physics & Astronomy and Department of Computer Science Louisiana State University Baton Rouge, LA 70803-4001 DONALD W. BRENNER Department of Materials Science and Engineering North Carolina State University Raleigh, NC 27695
ABSTRACT Using a reactive empirical bond-order potential (REBOP) model for hydrocarbons], large scale molecular dynamics simulations of carbon systems are carried out on parallel machines. Structural and dynamical correlations of amorphous carbon at various densities are studied. The calculated structure factor agrees well with neutron scattering experiments and the results of tightbinding molecular dynamics simulations. The dynamic behavior of crack propagation through graphite sheet is also investigated with the molecular-dynamics method. Effects of external stress and initial notch shape on crack propagation in graphite are studied. It is found that graphite sheet fractures in a cleavage-like or branching manners depending on the orientations of the graphite sheet with respect to the external stress. The roughness of crack surfaces is analyzed. Two roughness exponents are observed in two different regions. INTRODUCTION Carbon is unique among all the elements in that it can form strong covalent bonds with various coordination numbers. Carbon can not only form many different kinds of chemical compounds, it also has a rich structure and complex phase diagrams. New structures of carbon, such as fullerenes and graphitic tubules, and various new compounds of carbon are continuously being discovered. Despite intensive experimental and theoretical studies, 2 -11 there remain a lot questions and problems. The understanding of the connection between the microscopic structure and the physical properties of carbon systems is still far from complete. So far most ab initio approach and tightbinding 7 -10 simulation studies of carbon systems have focused on the structure and electronic properties. These approaches are highly accurate, but they are usually limited to relatively small systems. We focus our attention on structural and mechanical properties of carbon system in the nanometer regime. We choose a classical approach for practical. Although we may lose some detail information about the electronic structures, we try to keep the approximation as accurate as possible. The model we use in our simulations is called reactive empirical bond-order potential (REBOP) model developed recently by Brenner, et al.I Using the REBOP model, we have recently carried out large-scale molecular-dynamics simulations to study various forms of carbon systems including amorphous carbon and graphite.
113 Mat. Res. Soc. Symp. Proc. Vol. 408 © 1996 Materials Research Society
Structural and dynamical correlations of amorphous carbon at various densities are investigated. The dynamic behavior of crack propagation through graphite sheet is also investigated with the molecular-dynamics method. In this
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