Molecular orbital theory of the properties of inorganic and organometallic compounds 4. Extended basis sets for third‐and fourth‐row, main‐group elements

Abstract

Abstract Two new series of efficient basis sets for third‐ and fourth‐row, main‐group elements have been developed. Split‐valence 3‐21G basis sets have been formulated from the minimal expansions by Huzinaga, in which each atomic orbital has been represented by a sum of three Gaussians. The original expansions for s − and p −type orbitals (except those for 1 s ) have been replaced by new combinations in which the two sets of orbitals (of the same n quantum number) share Gaussian exponents. The Huzinaga expansions for 1 s , 3 d and 4 d (fourth‐row elements only) have been employed without further alteration. The valence atomic functions 4 s , 4 p for third‐row elements; 5 s , 5 p for fourth‐row elements have been split into two and one Gaussian parts. Supplemented 3‐21G (*) representations have been formed from the 3‐21G basis sets by the addition of a set of single d −type Gaussian functions. The performance of 3‐21G and 3‐21G (*) basis sets is examined with regard to the calculation of equilibrium geometries, normal mode vibrational frequencies, reaction energies, and electric dipole moments involving a variety of normal and hypervalent compounds containing third‐ and fourth‐row, main‐group elements. The supplementary functions incorporated into the 3‐21G (*) basis sets are generally found to be important, especially for the proper description of equilibrium bond lengths and electric dipole moments. 3‐21G (*) representations are recommended for general use in lieu of the unsupplemented 3‐21G basis sets.