Atomic orbital basis sets for use with effective core potentials

Abstract

ABSTRACT:Basis sets developed for use with effective core potentials describe pseudo-orbitals rather than orbitals. The primitive Gaussian functions and the contraction coefficients in the basis set must therefore both describe the valence region effectively and allow the pseudo-orbital to be small in the core region. The latter is particularly difficult using 1s primitive functions, which have their maxima at the nucleus. Several methods of choosing contraction coefficients are tried, and it is found that natural orbitals give the best results. The number and optimization of primitive functions are done following Dunning's correlation-consistent procedure. Optimization of orbital exponents for larger atoms frequently results in coalescence of adjacent exponents; use of orbitals with higher principal quantum number is one alternative. Actinide atoms or ions provide the most difficult cases in that basis sets must be optimized for valence shells of different radial size simultaneously considering correlation energy and spin-orbit energy.

Gaussian basis sets for use in correlated molecular calculations. XI. Pseudopotential-based and all-electron relativistic basis sets for alkali metal (K–Fr) and alkaline earth (Ca–Ra) elements

“…An additional s function was also uncontracted for the PP-based sets as single uncontracted primitive functions recover less correlation energy when using PPs than in the all-electron case. 37,39,40 This was also tested for p functions, but the incremental correlation energy lowering was small and extra uncontracted p primitives were not included in the current case. The resulting total correlating functions uncontracted from the HF primitives for the PP based sets were (2s1p1d), (3s2p2d), (4s3p3d), and (5s4p4d) for DZ-5Z, respectively.…”

Atomic self-consistent-field program by the basis set expansion method: Columbus version

“…Thus s 1 p 3 5 S appears in the intershell table as p 3 ( 4 S)s 1 ( 2 S) 5 1. λ N Oλ 1 S states with seniority 0. These are usually the highest-energy states from this electron configuration.…”

“…(continued on next page) 10 G −8 g 9 ( 10 S) s 1 ( 2 S) 11 S −9 g 9 ( 10 S) s 1 ( 2 S) 9 S 11 J 212 K 211 K 213 2 or 14 d, p electrons 3 5 . The present calculation was used to obtain the s, p, and d contractions together.…”

“…The features of the program will be described principally with respect to the original Chicago version. The principal use of this program has been for developing basis sets for molecular calculations [4][5][6].…”

The generality of the GUGA MRCI approach in COLUMBUS for treating complex quantum chemistry

“…Compact correlation-consistent double zeta plus polarization basis sets developed for use with RECPs, and SO operators were employed. 130 Large reference spaces consisting of the fully occupied 1u, 2u, 3u MOs and the partially occupied 1u, 1u, 3u…”