Relativistic correlating basis sets for the main group elements from Cs to Ra

Abstract

Contracted Gaussian-type function sets are developed for correlating functions of the ten main group elements from Cs to Ra. A segmented contraction scheme is used for its compactness and efficiency. Contraction coefficients and exponents are determined by minimizing the deviation from accurate natural orbitals or K-orbitals, incorporating the relativistic effect by the third-order Douglas–Kroll approximation. The present basis sets yield more than 98% of atomic correlation energies predicted by accurate natural orbitals of the same size. The use of the present set with the model core potential methods gives more than 99% of the correlation energies obtained by the atomic natural orbitals optimized for the model core potential itself. The present correlating sets applied to relativistic model core potential methods including spin–orbit effects predict the spectroscopic constants of the BiH molecule in excellent agreement with experimental results.