Relativistic quintuple-zeta basis sets for the s block

Relativistic basis sets of quintuple-zeta quality are presented for the s-block elements. The basis sets include self-consistent field exponents for the occupied spinors and for the np shell (the latter is considered here a valence orbital). Valence and core correlating functions were optimized within multireference singles and doubles configuration interaction calculations for the ground valence configuration. Diffuse functions optimized for the corresponding anions or derived from neighboring elements are also provided. The new basis sets were applied to a range of basic atomic and molecular properties for benchmarking purposes. Smooth convergence to the basis set limit is observed with increased basis set quality from existing double-zeta, triple-zeta, and quadruple-zeta to the newly developed quintuple-zeta basis sets. The use of these basis sets, in combination with state-of-the-art approaches for the treatment of relativity and correlation, will allow achieving higher accuracy and lower uncertainty than previously possible in calculations on heavy atoms and molecules. The basis sets are available at https://doi.org/10.5281/zenodo.17088050.