Correlation consistent basis sets for molecular core-valence effects with explicitly correlated wave functions: The atoms B–Ne and Al–Ar

Abstract

Correlation consistent basis sets have been optimized for accurately describing core-core and core-valence correlation effects with explicitly correlated F12 methods. The new sets, denoted cc-pCVnZ-F12 (n=D, T, Q) and aug-cc-pC(F12)VnZ (n=D, T, Q, 5), were developed by augmenting the cc-pVnZ-F12 and aug-cc-pVnZ families of basis sets with additional functions whose exponents were optimized based on the difference between all-electron and valence-electron correlation energies. The number of augmented functions added is fewer, in general, than in the standard cc-pCVnZ and cc-pwCVnZ families of basis sets. Optimal values of the geminal Slater exponent for use with these basis sets in MP2-F12 calculations are presented and are also recommended for CCSD-F12b calculations. Auxiliary basis sets for use in the resolution of the identity approximation in explicitly correlated calculations have also been optimized and matched to the new cc-pCVnZ-F12 series of orbital basis sets. The cc-pCVnZ-F12 basis sets, along with the new auxiliary sets, were benchmarked in CCSD(T)-F12b calculations of spectroscopic properties on a series of homo- and heteronuclear first and second row diatomic molecules. Comparing the effects of correlating the outer core electrons in these molecules with those from conventional CCSD(T) at the complete basis set limit, which involved calculations with new cc-pCV6Z basis sets for the second row elements that were also developed in the course of this work, it is observed that the F12 values are reasonably well converged already at just the triple-zeta level.

Gaussian basis sets for molecular applications

“…[214] The resulting OptRI ABSs are compact and produce negligible RI errors compared to the basis set incompleteness error of the underlying OBS, both for correlation and relative energies. Although originally published to match the cc-pVnZ-F12 bases, the same methodology has been used to produce OptRI sets specifically matched to aug-cc-pVnZ bases, [215] to cc-pCVnZ-F12 bases, [51] for the light alkali and alkaline earth elements, [95] and for the group 11 and 12 transition metal elements. [186] It has been observed that while these OptRI basis sets are not optimal for producing the largest CABS singles energy corrections, if relative energies are considered the OptRI sets in conjunction with CABS singles corrections are sufficient to practically eliminate the HF basis set error.…”

“…[96,97] Correlation consistent basis sets for accurately describing core-core and core-valence correlation in an F12 framework have also been published for the elements LiAAr. [51,95] Two alternatives were proposed and denoted cc-pCVnZ-F12 and aug-cc-pC F12 VnZ, based on adding tight functions to the ccpVnZ-F12 and aug-cc-pVnZ basis sets, respectively. The number of additional functions added to construct the cc-pCVnZ-F12 sets is very small, especially at the QZ level, where only [1s1p1d] are added (for the first row elements), compared to [3s3p2d1f ] in aug-cc-pCVnZ.…”

“…For high-accuracy studies, it is frequently important to correlate at least an additional shell of core electrons, which requires a number of tight functions optimized for this purpose. There are two established approaches for optimizing such exponents; in the cc-pCVnZ basis sets, the exponents are optimized based on the difference between valence-only and core and valence correlation energies, [48][49][50][51] whereas in the ccpwCVnZ bases, the core-valence contribution to the correlation energy is strongly weighted over the core-core (hence the w in the basis set abbreviation). [49,50] Typically, the cc-pwCVnZ sets produce better results for small zeta, with the results from both approaches converging rapidly for larger basis sets.…”

Simulation of the single-vibronic-level emission spectra of HAsO and DAsO

“…In these MRCI-F12 calculations, which correlated also the As 3d 10 electrons, the geminal Slater exponent {β, in the nonlinear correlation factor, F (r 12 ) = -(1/β)exp(-βr 12 )} was set to 1.5 instead of the default value of 1.0 used for valence only calculations, as recommended for core-valence F12 calculations. 35 With the default frozen core, the total numbers of contracted and uncontracted configurations used in the MRCI-F12 calculations are 1516432 and 138334504, respectively. With the As 3d 10 electrons also active in the MRCI-F12…”

Relaxation of energetic S(1D) atoms in Xe gas: Comparison of ab initio calculations with experimental data

“…20 The dynamic polarizabilities of S( 1 D) were obtained from the linear response MC-SCF theory 17 as implemented in DALTON quantum chemistry program. 18 The active space in this MCSCF calculation is defined as 6 electrons distributed in 13 MOs, which include 3s3p3d4s4p of S. The d-aug-cc-pCV6Z basis set 19 was employed in the MCSCF calculation. For Xe, we adopted the accurate values obtained from the relativistic many-body calculations in Ref.…”