Pressure-induced rotation-libration transition in molecular solid hydrogen. A comparison between interaction potentials

Abstract

The pressure-induced rotation-libration transition in solid molecular para-H2 and ortho-D2 is calculated using anisotropic nearest neighbor interaction potentials of the formVij=Σ m C m (r ij )Y2m(Ω i )Y2−m(Ωj). The contribution of variousm terms is investigated. It is found that, for a trial wave function of Jastrow type, the expectation of them=1 term vanishes, while the ratio between the expectations of them=0 andm=2 terms is a rational numerical constant. The trial wave function incorporates two variational parameters and the variational integrals are evaluated by a Monte Carlo procedure. The potentials of Ree and Bender, and of Van Kranendonk and Nakamura were compared to each other. The Ree and Bender potential seems to be better suited for describing high-density properties, although the transition pressure turned out to be well above the experimental value.