The correlation‐consistent polarized valence basis sets (cc‐pVXZ) for the atoms boron through neon have been extended to treat core and core‐valence correlation effects. Basis functions were added to the existing cc‐pVXZ sets to form correlation‐consistent polarized core‐valence sets (cc‐pCVXZ) in the usual pattern: Double zeta added (1s1p), triple zeta added (2s2p1d), quadruple zeta added (3s3p2d1f), and quintuple zeta added (4s4p3d2f1g). The exponents of the core functions were determined by minimizing the difference between all‐electron and valence‐only correlation energies obtained from HF+1+2 calculations on the ground states of the atoms. With the cc‐pCVXZ sets, core, core‐valence, and valence correlation energies all converge exponentially toward apparent complete basis set (CBS) limits, as do the corresponding all‐electron singles and doubles CI energies. Several test applications of the new sets are presented: The first two ionization potentials of boron, the 3P–5S separation in carbon, and the X...

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Gaussian basis sets for use in correlated molecular calculations. V. Core-valence basis sets for boron through neon

The basis-set convergence of the electronic correlation energy in the water molecule is investigated at the second-order Mo/ller–Plesset level and at the coupled-cluster singles-and-doubles level with and without perturbative triples corrections applied. The basis-set limits of the correlation energy are established to within 2 mEh by means of (1) extrapolations from sequences of calculations using correlation-consistent basis sets and (2) from explicitly correlated calculations employing terms linear in the interelectronic distances rij. For the extrapolations to the basis-set limit of the correlation energies, fits of the form a+bX−3 (where X is two for double-zeta sets, three for triple-zeta sets, etc.) are found to be useful. CCSD(T) calculations involving as many as 492 atomic orbitals are reported.

Basis-set convergence of correlated calculations on water

Valence correlation consistent and augmented correlation consistent basis sets have been determined for the third row, main group atoms gallium through krypton. The methodology, originally developed for the first row atoms, was first applied to the selenium atom, resulting in the expected natural groupings of correlation functions (although higher angular momentum functions tend to be relatively more important for the third row atoms as they were for the second row atoms). After testing the generality of the conclusions for the gallium atom, the procedure was used to generate correlation consistent basis sets for all of the atoms gallium through krypton. The correlation consistent basis sets for the third row main group atoms are as follows: cc-pVDZ: (14s11p6d)/[5s4p2d]; cc-pVTZ: (20s13p9d1f )/[6s5p3d1f]; cc-pVQZ: (21s16p12d2 f1g)/[7s6p4d2 f1g]; cc-pV5Z: (26s17p13d3f2g1h)/[8s7p5d3f2g1h]. Augmented sets were obtained by adding diffuse functions to the above sets (one for each angular momentum present in the set), with the exponents of the additional functions optimized in calculations on the atomic anions. Test calculations on the atoms as well as selected molecules with the new basis sets show good convergence to an apparent complete basis set limit.

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Gaussian basis sets for use in correlated molecular calculations. IX. The atoms gallium through krypton

A role for electronic structure databases in assisting users of quantum chemistry applications select better model parameters is discussed in light of experiences gained from a software prototype known as the Computational Chemistry Input Assistant (CCIA). It is argued that the ready availability of information pertaining to the applications and theoretical models can substantially increase the likelihood of novice users obtaining the desired accuracy from their calculations while simultaneously making better use of computer resources. Expert users, who find themselves contemplating studies in new areas of research, may also benefit from the proposed tools. For maximum impact, this assistance should be provided while users are actively engaged in preparing calculations. © 1996 by John Wiley & Sons, Inc.

The role of databases in support of computational chemistry calculations

A series of correlation consistent basis sets have been developed for the post-d group 16–18 elements in conjunction with small-core relativistic pseudopotentials of the energy-consistent variety. The latter were adjusted to multiconfiguration Dirac–Hartree–Fock data based on the Dirac–Coulomb–Breit Hamiltonian. The outer-core (n−1)spd shells are explicitly treated together with the nsp valence shell with these PPs. The accompanying cc-pVnZ-PP and aug-cc-pVnZ-PP basis sets range in size from DZ to 5Z quality and yield systematic convergence of both Hartree–Fock and correlated total energies. In addition to the calculation of atomic electron affinities and dipole polarizabilities of the rare gas atoms, numerous molecular benchmark calculations (HBr, HI, HAt, Br2, I2, At2, SiSe, SiTe, SiPo, KrH+, XeH+, and RnH+) are also reported at the coupled cluster level of theory. For the purposes of comparison, all-electron calculations using the Douglas–Kroll–Hess Hamiltonian have also been carried out for the haloge...

http://tyr0.chem.wsu.edu/~kipeters/Pages/pdfs/JCP119.11113.2003.pdf

Systematically convergent basis sets with relativistic pseudopotentials. II. Small-core pseudopotentials and correlation consistent basis sets for the post-d group 16–18 elements

An accurate description of the electrical properties of atoms and molecules is critical for quantitative predictions of the nonlinear properties of molecules and of long‐range atomic and molecular interactions between both neutral and charged species. We report a systematic study of the basis sets required to obtain accurate correlated values for the static dipole (α1), quadrupole (α2), and octopole (α3) polarizabilities and the hyperpolarizability (γ) of the rare gas atoms He, Ne, and Ar. Several methods of correlation treatment were examined, including various orders of Moller–Plesset perturbation theory (MP2, MP3, MP4), coupled‐cluster theory with and without perturbative treatment of triple excitations [CCSD, CCSD(T)], and singles and doubles configuration interaction (CISD). All of the basis sets considered here were constructed by adding even‐tempered sets of diffuse functions to the correlation consistent basis sets of Dunning and co‐workers. With multiply‐augmented sets we find that the electrical properties of the rare gas atoms converge smoothly to values that are in excellent agreement with the available experimental data and/or previously computed results. As a further test of the basis sets presented here, the dipole polarizabilities of the F− and Cl− anions and of the HCl and N2 molecules are also reported.

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Gaussian basis sets for use in correlated molecular calculations. IV. Calculation of static electrical response properties

Benchmark calculations employing the correlation consistent basis sets of Dunning and co‐workers are reported for the following diatomic species: Al2, Si2, P2, S2, Cl2, SiS, PS, PN, PO, and SO. Internally contracted multireference configuration interaction (CMRCI) calculations (correlating valence electrons only) have been performed for each species. For Cl2, P2, and PN, calculations have also been carried out using Mo/ller–Plesset perturbation theory (MP2, MP3, MP4) and the singles and doubles coupled‐cluster method with and without perturbative triples [CCSD, CCSD(T)]. Spectroscopic constants and dissociation energies are reported for the ground state of each species. In addition, the low‐lying excited states of Al2 and Si2 have been investigated. Estimated complete basis set (CBS) limits for the dissociation energies, De, and other spectroscopic constants are obtained from simple exponential extrapolations of the computed quantities. At the CBS limit the root‐mean‐square (rms) error in De for the CMRCI...

Thorn H. Dunning

Papers

Gaussian basis sets for use in correlated molecular calculations. IV. Calculation of static electrical response properties

Benchmark calculations with correlated molecular wave functions. VI. Second row A2 and first row/second row AB diatomic molecules