ANHARMONIC LATTICE-VIBRATIONS IN PALLADIUM

Macroscopic and microscopic effects of anharmonic lattice vibrations in Pd have been studied. The interatomic forces are modelled according to a phenomenological potential which includes three-body angular forces in the harmonic part. The cubic and quartic force constants are fitted to the experimental linear thermal expansion coefficient and constant-pressure specific heat, respectively. Thermoelastic properties are evaluated in quasi-harmonic approximation while caloric properties require computation of constant-volume anharmonic contributions. The phonon lineshifts and linewidths have been calculated along the principal symmetry directions, in the framework of the second-order perturbation theory. The room-temperature experimental anomalies in the (ξξ0)T1 branch are reproduced by the theory. © 1990 IOP Publishing Ltd.