On the Specialisation of Gaussian Basis Sets for Core-Dependent Properties

TL;DR

This paper evaluates the effectiveness of core-specialised Gaussian basis sets in accurately modeling core-dependent properties in quantum chemistry, showing significant error reduction over general-purpose sets with minimal computational cost increase.

Contribution

It compares and recommends specific core-specialised basis sets for accurate calculation of core-dependent properties, highlighting their advantages over standard basis sets.

Findings

Core-specialised basis sets reduce errors significantly.

Recommended basis sets for different properties are identified.

Marginal increase in computational cost with improved accuracy.

Abstract

Despite the fact that most quantum chemistry basis sets are designed for accurately modelling valence chemistry, these general-purpose basis sets continue to be widely used to model core-dependent properties. Core-specialised basis sets are designed with specific features to accurately represent the behaviour of the core region. This design typically incorporates Gaussian primitives with higher exponents to capture core behaviour effectively, as well as some decontraction of basis functions to provide flexibility in describing the core electronic wave function. The highest Gaussian exponent and the degree of contraction for both $s$- and $p$-basis functions effectively characterise these design aspects. In this study, we compare the design and performance of general-purpose basis sets against several literature basis sets specifically designed for three core-dependent properties: J coupling constants, hyperfine coupling constants, and magnetic shielding constants (used for calculating chemical shifts). Our findings consistently demonstrate a significant reduction in error when employing core-specialised basis sets, often at a marginal increase in computational cost compared to the popular 6-31G** basis set. Notably, for expedient calculations of J coupling, hyperfine coupling and magnetic shielding constants, we recommend the use of the pcJ-1, EPR-II, and pcSseg-1, basis sets respectively. For higher accuracy, the pcJ-2, EPR-III, and pcSseg-2 basis sets are recommended.