Abstract
New correlation consistent basis sets based on pseudopotential (PP) Hamiltonians have been developed from double- to quintuple-zeta quality for the late alkali (K-Fr) and alkaline earth (Ca-Ra) metals. These are accompanied by new all-electron basis sets of double- to quadruple-zeta quality that have been contracted for use with both Douglas-Kroll-Hess (DKH) and eXact 2-Component (X2C) scalar relativistic Hamiltonians. Sets for valence correlation (ms), cc-pVnZ-PP and cc-pVnZ-(DK,DK3/X2C), in addition to outer-core correlation [valence + (m-1)sp], cc-p(w)CVnZ-PP and cc-pwCVnZ-(DK,DK3/X2C), are reported. The -PP sets have been developed for use with small-core PPs [I. S. Lim et al., J. Chem. Phys. 122, 104103 (2005) and I. S. Lim et al., J. Chem. Phys. 124, 034107 (2006)], while the all-electron sets utilized second-order DKH Hamiltonians for 4s and 5s elements and third-order DKH for 6s and 7s. The accuracy of the basis sets is assessed through benchmark calculations at the coupled-cluster level of theory for both atomic and molecular properties. Not surprisingly, it is found that outer-core correlation is vital for accurate calculation of the thermodynamic and spectroscopic properties of diatomic molecules containing these elements.
Highlights
Molecular electronic structure calculations are typically carried out using one-particle basis sets of Gaussian-type functions, and the incompleteness of this basis can be a major source of error.1–3 addressing this problem by using the largest possible basis results in poor efficiency and is restrictive in terms of tractable system size; families of basis sets that systematically approach the complete basis set (CBS) limit have been developed
For all-electron calculations, the atomic natural orbital (ANO) basis sets of Roos and co-workers,20 denoted ANO-RCC, the Dirac-Coulomb relativistic correlation consistent sets of Dyall,21 and the Sapporo natural orbital based segmented contracted Gaussian (NOSeC) sets of Noro et al are available in a range of sizes from DZ to QZ.22
coupled cluster singles and doubles (CCSD) with perturbative triples, CCSD(T), was generally used to obtain these properties, calculations using the standard “valence-only” basis sets used a frozen core definition that meant only the ms electrons were correlated and the level of theory is equivalent to HF or CCSD for group 1 and 2, respectively
Summary
Molecular electronic structure calculations are typically carried out using one-particle basis sets of Gaussian-type functions, and the incompleteness of this basis can be a major source of error. addressing this problem by using the largest possible basis results in poor efficiency and is restrictive in terms of tractable system size; families of basis sets that systematically approach the complete basis set (CBS) limit have been developed. For all-electron calculations, the atomic natural orbital (ANO) basis sets of Roos and co-workers, denoted ANO-RCC, the Dirac-Coulomb relativistic correlation consistent sets of Dyall, and the Sapporo natural orbital based segmented contracted Gaussian (NOSeC) sets of Noro et al are available in a range of sizes from DZ to QZ.22 In addition to the above basis sets, there are a number of notable sets available for the 4s–6s s-block elements Those paired to PPs include the Los Alamos National Laboratory (LANL) double zeta basis, denoted LANL2DZ, and the uncontracted revised basis LANL08.24 The segmented contracted DZ through QZ quality sets of Weigend and Ahlrichs (often referred to as the def family of basis sets) are paired to Wood-Boring type PPs for the 5s and 6s elements, with all-electron sets for 4s.25. In addition to the above sets optimized for the treatment of valence (ms) electron correlation, sets for the recovery of the (m 1)sp correlation effects are presented
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