Inelastic neutron scattering in solid neon at high pressure

The phonon dispersion relations in a high density Ne crystal have been measured in the 100, 110, and 111 symmetry directions at 8 K using a triple axis neutron spectrometer. The data is analyzed using harmonic Born-von Karman force constants with the result that the interatomic forces in this Ne crystal are predominantly central in nature. The data is found to be well represented in the harmonic approximation by a Lennard-Jones potential. A dispersion of mode Grueneisen parameters is used to obtain the macroscopic Grueneisen parameter. Comparisons are given with theoretical calculations. Quasiharmonic calculations are shown to over estimate the volume dependence of the phonon energies. Thermodynamic analysis using the density of phonon states shows the decreased importance of zero-point motion in the high density crystal.