Dirac-fock basis set calculations for atoms and molecules

Abstract

We present Dirac‐Hartree‐Fock (DHF) atomic structure calculations of many‐electron atoms (Z=2−86) using kinetically balanced geometric basis sets of Gaussian functions. It is seen that ‘‘variational collapse’’ or bound failure does not occur if we impose the condition of kinetic balance between the large and the small component spinors along with proper boundary conditions for bound state orbitals. Furthermore, with a finite size nucleus model the DHF total energy for atoms converges more rapidly to the numerical Dirac‐Fock (DF) limit with a fewer number basis functions than those calculations where point nucleus is assumed. By systematically extending the geometric basis sets, we have obtained the DHF total energies for all atoms (upto Z=86) within a few millihartrees of the numerical (DF) limit, with smooth convergence from above.We also demonstrate the use of kinetically‐balanced geometric Gaussian basis functions in DHF molecular structure calculations.