N-body interatomic potentials for hexagonal close-packed metals

Abstract

Abstract Finnis-Sinclair (F-S) type many-body potentials have been constructed for eight hexagonal metals: Co, Zr, Ti, Ru, Hf, Zn, Mg and Be. The potentials are parameterized using cubic splines and fitted to the cohesive energy, unrelaxed vacancy formation energy, five independent second-order elastic constants and two eauilibrium conditions. Hence, each of the constructed potentials represents a stable hexagonal close-packed lattice with a particular non-ideal c/a ratio. In the F-S scheme the many-body part is represented by a sauare root function and this form implies that C12 – C66>0. However, C 12 –C66 is negative for Zn, Be and Ru at Iow temperatures. For this reason a modified many-body function has been employed for these metals. To ensure the applicability of the potentials in modelling of extended lattice defects, the mechanical stability of the corresponding hexagonal close-packed lattice with respect to large homogeneous deformations has been tested. For all the metals considered, the h.c.p. l...