Attachment of Hydrogen Molecules to Atomic Ions (Na+, Cl-): Examination of an Adiabatic Separation of the H2 Rotational Motion

Interactions between molecular hydrogen and ions are of interest in cluster science, astrochemistry and hydrogen storage. In dynamical simulations, H-2 molecules are usually modelled as point particles, an approximation that can fail for anisotropic interactions. Here, we apply an adiabatic separation of the H-2 rotational motion to build effective pseudoatom-ion potentials and in turn study the properties of (H-2)(n)Na+/Cl- clusters. These interaction potentials are based on high-level ab initio calcu- lations and Improved Lennard-Jones parametrizations, while the subsequent dynamics has been performed by quantum Monte Carlo calculations. By comparisons with simulations explicitly describing the molecular rotations, it is concluded that the present adiabatic model is very adequate. Interestingly, we find differences in the cluster stabilities and coordination shells depending on the spin isomer considered (para- or ortho-H-2), especially for the anionic clusters.

Automated summary

In this study, an adiabatic separation of the rotational motion of H2 molecules is applied to build effective pseudoatom-ion potentials for (H2)nNa+/Cl- clusters. The accuracy of this adiabatic model is confirmed by comparing with simulations that explicitly describe molecular rotations. Additionally, differences in cluster stabilities and coordination shells are found depending on the spin isomer, particularly for anionic clusters.