Adequacy of lattice dynamics for high-temperature point-defect properties

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Abstract
Comparison with existing Monte Carlo and molecular-dynamics data of novel quasiharmonic lattice-dynamics (LD) calculations for formation and migration of lattice vacancies in rare-gas crystals at melting shows that the effect of residual anharmonicity on atomic diffusion is not large. Inclusion of vibrational contributions to the free energy and pressure ensures, for the first time, thermodynamic consistency between LD results at constant volume, pressure, and lattice spacing. Lattice-statics predictions are badly in error. Constant-volume defect entropies are negative and surprisingly large.