Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen

Abstract

In the past, basis sets for use in correlated molecular calculations have largely been taken from single configuration calculations. Recently, AlmlOf, Taylor, and co-workers have found that basis sets of natural orbitals derived from correlated atomic calculations (ANOs) provide an excellent description of molecular correlation effects. We report here a careful study of correlation effects in the oxygen atom, establishing that compact sets of primitive Gaussian functions effectively and efficiently describe correlation effects if the exponents of the functions are optimized in atomic correlated calculations, although the primitive (sp) functions for describing correlation effects can be taken from atomic Hartree-Fock calculations if the appropriate primitive set is used. Test calculations on oxygen-containing molecules indicate that these primitive basis sets describe molecular correlation effects as well as the ANO sets of Alml6f and Taylor. Guided by the calculations on oxygen, basis sets for use in correlated atomic and molecular calculations were developed for all of the first row atoms from boron through neon and for hydrogen. As in the oxygen atom calculations, it was found that the incremental energy lowerings due to the addition of correlating functions fall into distinct groups. This leads to the concept of correlation consistent basis sets, i.e., sets which include all functions in a given group as well as all functions in any higher groups. Correlation consistent sets are given for all of the atoms considered. The most accurate sets determined in this way, [5s4p3d 2flg] , consistently yield 99% of the correlation energy obtained with the corresponding ANO sets, even though the latter contains 50% more primitive functions and twice as many primitive polarization functions. It is estimated that this set yields 94%-97% of the total (HF + 1 + 2) correlation energy for the atoms neon through boron.

Electronic Structure and Spectroscopy of Nucleic Acid Bases: Ionization Energies, Ionization-Induced Structural Changes, and Photoelectron Spectra

“…No symmetry constrains were imposed in geometry optimizations. For A, T and C, Dunning's cc-pVTZ basis set [36] was used, whereas for guanine we employed an extended cc-pVTZ+dff basis [37] augmented by additional s and p diffuse functions for the second row elements, and s-functions for hydrogen. The exponents were taken from 6-311(2+,+)G basis set.…”

“…The first approach may be affected by spin-contamination, whereas the latter accounts only for the small portion of electron correlation. The benchmark calculations for the five ionized states of uracil [44] VIEs and AIEs of A, T, and C were computed by EOM-IP-CCSD with the cc-pVTZ basis set [36]. For guanine, an augmented basis, cc-pVTZ+dff, and Frozen Natural Orbitals (FNO) approximation were employed [37].…”

Free-energy perturbation and quantum mechanical study of SAMPL4 octa-acid host–guest binding energies

“…Full counterpoise correction was used throughout. The cc-pVTZ basis set [76,77] was applied in these calculations. Density-fitting (DF) approximations [78,79] were used for both the Hartree-Fock and the correlation part, with the corresponding cc-pVTZ/JKFIT [80] and ccpVTZ/MP2FIT [81] auxiliary basis sets, respectively.…”

A computational study of the double hydrogen migration in the molecular ions of endo tricyclo[5.2.1.02,6]decene

“…The results were used in subsequent restricted open shell Hartree-Fock (ROHF) 4-31G optimi-zations of possible stable intermediates and transition states with GAMESS-UK [2]. These were used as starting points for more accurate density functional calculations using Gaussian 98 [3] with the B3LYP functional with Dunning's cc-pVDZ (correlation consistent polarized double zeta) basis set [4]. Transition states were tested by a visualization of the vibration corresponding with the single imaginary frequency with VIBRAM [5] or by intrinsic reaction coordinate (IRC) calculations.…”