The phonon absorption line shape of solid molecular H2 and D2 as a function of density

A theoretical study is presented of the lattice dynamics of the cubic phases of solid hydrogen and deuterium as a function of density. The calculations are performed in the self-consistent phonon approximation and include cubic three-phonon processes and higher anharmonic corrections. The anisotropic part of the intermolecular potential is neglected and libronic effects are not included. The line shape of the one-phonon far-infrared absorption process is studied in detail and is found to display a complex and interesting behavior as a function of pressure. The experimental absorption line is well accounted for by the one-phonon line shapes calculated here and phonon-libron and multi-phonon absorption, which has been treated elsewhere. Phonon dispersion curves and elastic constants are also presented.Partial financial support provided by the Dutch Foundation for Fundamental Research of Matter (FOM).