Analytic modified embedded atom potentials for HCP metals

Analytic modified embedded atom method (AMEAM) type many-body potentials ha ve been constructed for ten hcp metals: Be, Co, Hf, Mg, Re, Ru, Sc, Ti, Y a nd Zr. The potentials are parametrized using analytic functions and fitted to the cohesive energy, unrelaxed vacancy formation energy, five independen t second-order elastic constants and two equilibrium conditions. Hence, eac h of the constructed potentials represents a stable hexagonal close-packed lattice with a particular non-ideal cia ratio. In order to treat the metals with negative Cauchy pressure, a modified term has been added to the total energy. For all the metals considered, the hcp lattice is shown to be ener getically most stable when compared with the fee and bcc structure and the hcp lattice with ideal c/a. The activation energy for vacancy diffusion in these metals has been calculated. They agree well with experimental data av ailable and those calculated by other authors for both monovacancy and diva cancy mechanisms and the most possible diffusion paths are predicted. Stack ing fault and surface energy have also been calculated and their values are lower than typical experimental data. Finally, the self-interstitial atom (SIA) formation energy and volume have been evaluated for eight possible si tes. This calculation suggests that the basal split or crowdion is the most stable configuration for metals with a rather large deviation from the ide al c/a value and the non-basal dumbbell (C or S) is the most stable configu ration for metals with cia near ideal. The relationship between SIA formati on energy and melting temperature roughly obeys a linear relation for most metals except Ru and Re.