Vibron Excitations in Solid Hydrogen: A Generalized Binary Random Alloy Problem

Abstract

Numerical calculations and Raman scattering measurements show that the vibrons in para-ortho mixtures of hydrogen are analogs of the one-electron states of a binary random alloy within the tight-binding Hamiltonian. Classical and Anderson-localized vibrons give important contributions to the spectral line shapes, which we demonstrate for a $\sim 20\%$ ortho mixture close to the percolation limit at zero pressure. Based on a Hamiltonian in which the hopping term is constrained by independent measurements, the theory also accurately predicts the evolution of the vibron spectra under pressure to 15 GPa.