Equation of state and Raman-activeE2glattice phonon in phases I, II, and III of solid hydrogen and deuterium

Abstract

We present results of lattice dynamics calculations of the $P$-$V$ equation of state and the pressure dependence of the Raman-active ${E}_{2g}$ lattice phonon for $p$-H${}_{2}$ and $o$-D${}_{2}$ in a wide pressure range up to $\ensuremath{\sim}$2 Mbars using our recently developed semiempirical many-body potential, and density-functional theory (DFT). Comparison with the existing body of experimental and theoretical results showed that the employed many-body potential is a reliable basis for high-precision calculations for phases I and II. For phase III it still works satisfactorily but the use of the DFT is preferable. The decomposition of the total energy and pressure into contributions from pair forces, three-body forces, and zero-point motion is presented.