The anisotropic interaction between hydrogen molecules

Abstract

The extent to which it is possible to estimate the anisotropic potential between two hydrogen molecules directly from ab initio calculations of the short range repulsive part of the interaction potential and the available semiempirical van der Waals and quadrupolar potentials is investigated. The anisotropic potential parameters ε₀(R), ε₂(R), ε₄(R), and B (R) due to nonquadrupolar anisotropic interactions are estimated for hydrogen in the range of intermolecular separations from 2.5 to 5 Å. At the nearest neighbor distance in solid hydrogen, R₀=3.756 Å, we recommend the following values ε₀=−0.002 cm⁻¹, ε₂=−0.027 cm⁻¹, ε₄=−0.016 cm⁻¹, and B=−0.310 cm⁻¹. At the next nearest neighbor distance of √2 R₀, we suggest ε₀=−0.0011 cm⁻¹, ε₂=−0.0017 cm⁻¹, ε₄=−0.0029 cm⁻¹, and B=−0.131 cm⁻¹.