Highly accurate relativistic universal Gaussian basis set for Dirac-Fock-Breit calculations

A universal Gaussian basis set is presented to perform highly accurate Dirac-Fock-Breit calculations. The Gaussian-type functions of our universal basis set satisfy the relativistic boundary conditions associated with the finite nucleus model, for a finite velocity of light, and conform to the so-called kinetic balance at the nonrelativistic limit. The high accuracy obtained in our Dirac-Fock-Breit calculations is attributed to the fact that with our universal Gaussian basis set we are able to better represent the relativistic kinematics of an electron inside the nucleus. Results for the Dirac-Fock-Breit energies for a number of neutral atoms up to nobelium and some of their negative ions are presented and compared with the results of Parpia et al., obtained by employing a geometrical Gaussian basis set and a more accurate value for the velocity of light. The Dirac-Fock-Breit energy results presented in this work, using our universal Gaussian basis set, are among the best obtained with Gaussian-type functions in the literature. (C) 2004 Wiley Periodicals, Inc. Int J Quantum Chem 102: 1-7, 2005.