All-electronXαself-consistent-field calculations of relativistic effects in the molecular properties ofTl2,fPb2, andBi2molecules

Abstract

Relativistic effects in the binding energy, the bond length, and vibrational frequencies of ground-state potential-energy curves are investigated for ${\mathrm{Tl}}_{2}$,${\mathrm{Pb}}_{2}$, and ${\mathrm{Bi}}_{2}$ by performing relativistic and nonrelativistic all-electron Dirac-Fock-Slater ${\mathrm{X}}_{\mathrm{\ensuremath{\alpha}}}$ calculations. Wave functions from numerical solutions of Dirac(Hartree)-Fock-Slater equations for atoms are taken as basis sets. A variationally consistent approximation for the direct Coulomb potential has been used for efficiently obtaining accurate potential energy curves. Our calculations confirm that the spin-orbit effect weakens the binding of the 6p-element molecules ${\mathrm{Tl}}_{2}$,${\mathrm{fPb}}_{2}$, and ${\mathrm{Bi}}_{2}$.