Hydrogen-Atom Electronic Basis Sets for Multicomponent Quantum Chemistry

TL;DR

This paper introduces optimized electronic basis sets for hydrogen in multicomponent quantum chemistry, improving accuracy and efficiency in describing electron-nuclear correlation and protonic properties.

Contribution

The study develops new correlation-consistent basis sets tailored for hydrogen nuclei, enhancing multicomponent calculations by better capturing electron-nuclear interactions.

Findings

New cc-pVnZ-mc basis sets outperform standard sets in protonic density accuracy.

Fewer basis functions needed for comparable accuracy with cc-pVnZ-mc sets.

Improved basis sets enable larger system calculations in multicomponent methods.

Abstract

Multicomponent methods are a conceptually simple way to include nuclear quantum effects into quantum chemistry calculations. In multicomponent methods, the electronic molecular orbitals are described using the linear combination of atomic orbitals approximation. This requires the selection of a one-particle electronic basis set which, in practice, is commonly a correlation-consistent basis set. In multicomponent method studies, it has been demonstrated that large electronic basis sets are required for quantum hydrogen nuclei to accurately describe electron-nuclear correlation. However, as we show in this study, much of the need for large electronic basis sets is due to the correlation-consistent electronic basis sets not being optimized to describe nuclear properties and electron-nuclear correlation. Herein, we introduce a series of correlation-consistent electronic basis sets for hydrogen atoms called cc-pVnZ-mc with additional basis functions optimized to reproduce multicomponent density functional theory protonic densities. These new electronic basis sets are shown to yield better protonic densities with fewer electronic basis functions than the standard correlation-consistent basis sets and reproduce other protonic properties such as proton affinities and protonic excitation energies, even though they were not optimized for these purposes. The cc-pVnZ-mc basis sets should enable multicomponent many-body calculations on larger systems due to the improved computational efficiency they provide for a given level of accuracy.