Pressure-Induced Intermolecular Interactions in Crystalline Silane-Hydrogen

The structure and dynamics of a recently discovered solid silane-hydrogen complex under high pressure are elucidated with first-principles molecular dynamics calculations. A structure with orientationally disordered silane and hydrogen with their centers of mass arranged in a distinctive manner are found. Natural bond orbital analysis reveals that perturbative donor-acceptor interactions between the two molecular species are enhanced by pressure. The experimentally observed anticorrelated pressure-frequency dependency is a consequence of these novel interactions. Moreover, the experimentally observed multiple Raman peaks of H-2 can be explained by temporal changes in the environment due to deviations of the lattice parameters from the ideal cubic lattice.