A. Canal Neto

Gaussian basis set of double zeta quality for atoms Rb through Xe: application in non-relativistic and relativistic calculations of atomic and molecular properties

The all-electron contracted Gaussian basis set of double zeta valence quality plus polarization functions (DZP) for the atoms from Rb to Xe is presented. The Douglas–Kroll–Hess (DKH) basis set for fourth-row elements is also reported. The original DZP basis set has been recontracted, i.e. the values of the contraction coefficients were re-optimized using the relativistic DKH Hamiltonian. This extends earlier works on segmented contracted DZ basis set for atoms H-Kr. These sets along with ab initio methods were used to calculate ionization energies of some atoms and spectroscopic constants of a sample of molecules and, then, comparison with results obtained with other basis sets was made. It was shown that experimental and benchmark bond lengths and harmonic vibrational frequencies can be reproduced satisfactorily with DZP-DKZ.

Gaussian basis set of triple zeta valence quality for the atoms from K to Kr: Application in DFT and CCSD(T) calculations of molecular properties

A contracted basis set of triple zeta (TZ) valence quality for the atoms from K to Kr was constructed from fully-optimized Gaussian basis sets generated in this work. Gaussian polarization functions (d, f, and g symmetries), which were optimized at the second-order Mφller–Plesset level, were added to the TZ set. This extends earlier work on segmented contracted TZ basis set for atoms H-Ar. This set along with the BP86 non-hybrid and B3LYP hybrid functionals were used to calculate geometric parameters, dissociation energy, harmonic vibrational frequency, and electric dipole moment of a sample of molecules and, then, comparison with results obtained with other basis sets and with experimental data reported in the literature is done. CCSD(T) atomic excitation energies and bond lengths, dissociation energies, and harmonic vibrational frequencies of some diatomics were also evaluated. Using density functional theory and gauge-including atomic orbitals, 57Fe and 77Se nuclear magnetic resonance chemical shifts in Fe(C5H5)2, H2Se, (CH3)SeH, CSe2, SeCO, H2CSe, and SeF6 were calculated. Comparison with theoretical and experimental values previously published in the literature was done. It is verified that in general these results give good agreement with experimental and benchmark values.

Adapted Gaussian basis sets for atoms Cs to Lr based on the generator coordinate Hartree–Fock method

We have applied a discretized version of the generator coordinate Hartree–Fock method to generate adapted Gaussian basis sets for atoms Cs (Z=55) to Lr (Z=103). Our Hartree–Fock total energy results, for all atoms studied, are better than the corresponding Hartree–Fock energy results attained with previous Gaussian basis sets. For the atoms Cs to Lr we have obtained an energy value within the accuracy of 10−4 to 10−3 hartree when compared with the corresponding numerical Hartree–Fock total energy results. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 858–865, 1998

Highly accurate relativistic gaussian basis sets for closed-shell atoms from He through to No

Abstract We have used the generator coordinate Dirac–Fock method for closed shell atoms, to generate accurate adapted Gaussian basis sets for ab initio relativistic self-consistent field calculations of some atoms from He (Z=2) through to No (Z=102). For all atoms studied, our Dirac–Fock–Coulomb and Dirac–Fock–Breit total energies are better than the corresponding ones obtained with previous larger Gaussian basis sets. Except for the Hg atom, our Dirac–Fock–Coulomb total energies are always equal to or lower than those calculated with the numerical finite-difference method (GRASP2 package). For No, we compare our Dirac–Fock–Coulomb and Dirac–Fock–Breit orbital energies with the corresponding values obtained with other approaches.

Some considerations about Dirac–Fock calculations

Abstract In this work, Gaussian basis sets are generated for closed-shell atoms from He ( Z =2) through No ( Z =102) to be used in Dirac–Fock atomic and molecular calculations. Dirac–Fock–Coulomb total energy values obtained with these wave functions are compared with those calculated using a universal Gaussian basis set and relativistic Gaussian basis sets. A discussion between these three approaches is presented. Besides this, we have found that for several atoms from He through Hg ( Z =80) the Dirac–Fock–Coulomb energies obtained with our wave functions are lower than the corresponding ones obtained with numerical-finite-difference calculations. A new procedure to generate Gaussian basis sets useful in relativistic calculations is suggested.