Benchmarking of the Fock space coupled cluster method and uncertainty estimation: Magnetic hyperfine interaction in the excited state of BaF

TL;DR

This paper evaluates the relativistic Fock-space coupled cluster method's accuracy in predicting hyperfine constants in BaF, emphasizing uncertainty estimation and comparison with experimental data.

Contribution

It provides a comprehensive assessment of the FSCC method's performance and uncertainty quantification for hyperfine structure calculations in molecules.

Findings

Good agreement between theory and experiment within uncertainties.

Higher basis set dependence and larger uncertainties in excited states.

Demonstrates the predictive power and reliability of the FSCC method.

Abstract

We present an investigation of the performance of the relativistic multi-reference Fock-space coupled cluster (FSCC) method for predicting molecular hyperfine structure (HFS) constants, including a thorough computational study to estimate the associated uncertainties. In particular, we considered the $^{19}$F HFS constant in the ground and excited states of BaF. Due to a larger basis set dependence, the uncertainties on the excited state results (16-85%) were found to be significantly larger than those on the ground state constants ($\sim$2%). The ab initio values were compared to the recent experimental results, and good overall agreement within the theoretical uncertainties was found. This work demonstrates the predictive power of the FSCC method and the reliability of the established uncertainty estimates, which can be crucial in cases where the calculated property cannot be directly compared to experiment.