Molecular dynamics (MD) is a computer simulation technique calculating time evolution of a set of interacting atoms or molecules by integrating relevant equations of motion. Each atom in the molecular dynamics is regarded to follow the laws of classical mechanics, mostly Newton’s law. The force acting on the motion of atoms mainly depends on the interatomic potential energy. Therefore, proper description of potential energy is the most important part in molecular dynamics simulations. The present KISSMD (Kinetic Simulation System based on molecular dynamics) program is based on the second nearest-neighbor modified embedded-atom method (2NN MEAM) interatomic potential formalism. |
Semi-empirical potential & modified embedded-atom method Semi-empirical interatomic potentials enable large-scale atomistic simulation useful in the study of solid-state phase transformations. In order to apply this technique to alloys, it is convenient to describe the atomic potentials of various elements with various crystal structures using a common formalism. The modified embedded atom method (MEAM) potential is the first semi-empirical interatomic potential formalism that showed the possibility that one single formalism can be applied to a wide range of elements including fcc, bcc, hcp, diamond-structured elements, and even gaseous elements. However, the originally published MEAM showed some critical shortcomings. For example, in the case of bcc elements, the bcc structure was not the most stable structure and other structures were created during MD runs at finite temperatures. |
M.I. Baskes, Phys. Rev. Lett. 59, 2666 (1987) M.I. Baskes, J.S. Nelson, and A.F. Wright, Phys. Rev. B 40, 6085 (1989) M.I. Baskes, Phys. Rev. B 46, 2727(1992) M.I. Baskes and R.A. Johnson, Modell. Simul. Mater. Sci. Eng. 2,147 (1994) |
Second nearest-neighbor modified embedded-atom method The problem of the MEAM in the description of bcc elements comes from the fact that the original MEAM considers only first nearest-neighbor interactions, by using a strong screening function. However, the second nearest-neighbor distance is larger than the first nearest-neighbor distance by only about 15% in the bcc structure. This means that interactions between second nearest-neighbor atoms in bcc may not be negligible. Therefore, the MEAM formalism was modified once again so that it can also consider the second nearest-neighbor interactions partially. Using this 2NN MEAM formalism, the problems found in the original MEAM for bcc elements and also other elements were solved. |
B.-J. Lee and M.I. Baskes, Phys. Rev. B 62, 8564(2000) B.-J. Lee, M.I. Baskes, H. Kim, and Y.K. Cho, Phys. Rev. B 64,184102 (2001) |
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2NN MEAM & KISSMD |
