Ionic displacement correlations from the zero-point motion of pressurized solid argon

We have performed first-principles calculations of the elastic constants and phonon dispersion for solid argon at pressures ranging from 3.1 GPa to 70 GPa. We also report our calculation of the spatial correlation function for the ground state and its pressure dependence. Arbitrary Cartesian displacements and lattice-site separations are considered. Analytical results, which rely only on knowledge of the elastic constants, are compared with results based on the calculated phonon dispersion throughout the Brillouin zone, and agree satisfactorily. The correlations are presented for pressures ranging from 3.1 GPa to 70 GPa, and the results suggest that the anharmonic character of the crystal’s ground state is more significant at low pressure.