Assessing weak hydrogen binding on Ca+ centers: An accurate many-body study with large basis sets

TL;DR

This study uses advanced quantum Monte Carlo methods with large basis sets to accurately predict weak hydrogen binding energies on calcium ions, revealing a double-well potential energy structure.

Contribution

It introduces an accurate many-body computational approach with large basis sets to study weak H2 binding on Ca+ centers, improving reliability of such predictions.

Findings

Predicted binding energy with a double-well structure.

Implemented efficient Hubbard-Stratonovich transformation with large basis sets.

Achieved accurate extrapolation to the complete basis set limit.

Abstract

Weak H2 physisorption energies present a significant challenge to even the best correlated theoretical many-body methods. We use the phaseless auxiliary-field quantum Monte Carlo (AFQMC) method to accurately predict the binding energy of Ca+ - 4H2. Attention has recently focused on this model chemistry to test the reliability of electronic structure methods for H2 binding on dispersed alkaline earth metal centers. A modified Cholesky decomposition is implemented to realize the Hubbard-Stratonovich transformation efficiently with large Gaussian basis sets. We employ the largest correlation-consistent Gaussian type basis sets available, up to cc-pCV5Z for Ca, to accurately extrapolate to the complete basis limit. The calculated potential energy curve exhibits binding with a double-well structure.