LATTICE-DYNAMICS, THERMAL-EXPANSION, AND 3RD-ORDER ELASTIC-CONSTANTS OF SEMINOBLE METALS

General expressions to calculate the first, second-, and third-order c oupling parameters considering a general interatomic model that includ es both two- and three-body uncoupled forces are given. These formulae are applied to deduce the analytic expressions of the pressure, the s econd-(SOEC), and third-order (TOEC) elastic constants and the dynamic al matrix and its strain derivative for the case of metals with face-c entred cubic (f.c.c.) structure and considering two-body interactions up to third neighbours and common nearest-neighbour three-body force o nes. A scheme of parametrization is proposed and the four independent parameters of the model are estimated. Within this framework the latti ce contribution to the dispersion curves, the TOEC's, and the Gruneise n function for Ni, Pd, and Pt are calculated and compared with the val ues obtained from experimental data. Also the microscopic information the model gives, particularly the importance of three-body forces and the fulfilment of the Gruneisen rule is analyzed.