Benchmarking ANO-R basis set for multiconfigurational calculations

The selection of basis sets is very important for multiconfigurational wave function calculation, due to a balance between a desired accuracy and computational costs. Recently, the atomic natural orbital-relativistic (ANO-R) basis set was published as a suggested replacement for the ANO-RCC basis set for scalar-relativistic correlated calculations Zobel et al (2021 J. Chem. Theory Comput. 16 278-294). Benchmarking ANO-R basis set against ANO-RCC for atoms (from H to Rn) and their compounds is the goal of this study. Many of these compounds (for instance, diatomic molecules containing transition metals) have open shells, for which reason a multiconfigurational approach is necessary and was primarily used throughout this project. Performance of the ANO-R basis set in multiconfigurational calculations is similar to the ANO-RCC basis set for the ionisation potential of atoms, and the bond distance in diatomic molecules. Deficiencies are noted for atomic electron affinities and dissociation energies of fluoride diatomic molecules. ANO-R basis sets are more compact in comparison to the corresponding ANO-RCC basis sets leading to smaller computational costs, which was demonstrated by chloroiron corrole molecule as an example.