Many-Body Potentials for Hexagonal Close-Packed Metals
Empirical many-body potentials are currently replacing pair potentials in studies of defects in metallic materials. The two widely used forms of potentials are the embedded-atom (Daw and Baskes 1984) and the Finnis-Sinclair types (Finnis and Sinclair 1984). Although these two approaches are based on different physical models, they reduce to very similar schemes on the empirical level (Johnson 1988). Recently, both approaches have been successfully used in a number of studies of defects in cubic transition and noble metals, most notably, in studies of surfaces (Daw and Baskes 1984, Ackland, Tichy, Vitek and Finnis 1987), point defects (Finnis and Sinclair 1984, Ackland et al. 1987) and cracks (Baskes, Foiles and Daw 1988). In these schemes, the total energy of a system of atoms consists of two parts, a many-body term and a pair potential, which are both determined by empirical fitting. An important point is that the many-body term plays a role analogous to that of the density dependent term in pair-potential schemes, but is now an explicit function of atomic positions. Hence, in contrast to pair-potentials, constant pressure calculations can be carried out straightforwardly and density variations can be easily accounted for.
KeywordsCohesive Energy Hexagonal Lattice Vacancy Formation Energy Optical Branch Order Elastic Constant
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