Accurate energies of transition metal atoms, ions, and monoxides using selected configuration interaction and density-based basis-set corrections

TL;DR

This paper enhances the accuracy of transition metal atom and molecule energies by combining the semistochastic heat-bath configuration interaction method with density-based basis-set corrections, achieving near-complete basis set results efficiently.

Contribution

It introduces a novel application of basis-set correction methods based on range-separated density-functional theory to accelerate convergence in SHCI calculations for transition metals.

Findings

Achieved near-complete basis set energies within chemical accuracy.

Significantly improved basis-set convergence speed.

Provided accurate ionization and dissociation energies for transition metal systems.

Abstract

The semistochastic heat-bath configuration interaction (SHCI) method is a selected configuration interaction plus perturbation theory method that has provided near-full configuration interaction (FCI) levels of accuracy for many systems with both single- and multi-reference character. However, obtaining accurate energies in the complete basis set limit is hindered by the slow convergence of the FCI energy with respect to basis size. Here we show that the recently developed basis-set correction method based on range-separated density-functional theory can be used to significantly speed up basis-set convergence in SHCI calculations. In particular, we study two such schemes that differ in the functional used, and apply them to transition metal atoms and monoxides to obtain total, ionization, and dissociation energies well converged to the complete-basis-set limit within chemical accuracy.