Lattice Dynamics with Three-Body Forces: Solid Xe and Kr

Phonon dispersion curves, elastic constants, and the pV isotherms are calculated for solid Xe and Kr at 0 K using quasiharmonic lattice dynamics derived from multiparameter pair potentials. The computations account for the Axilrod-Teller-Muto three-body triple-dipole forces that arise in third-order perturbation theory. Approximate allowance is also made for anharmonic effects and, in the case of Xe, for three-body, third-order, dipole-quadrupole interactions and the three-body dipole interactions that arise in fourth-order perturbation theory. The over-all agreement with experimental phonon data is good except, in the case of xenon, for the lowest-energy phonons in the [110] direction. This has the consequence that the shear elastic constant (C
11
− C
12
)/2 and the zero temperature Debye theta are somewhat lower than current experimental values.