Electronic structure for the ground state of TlH from relativistic multiconfiguration SCF calculations

Abstract

The dissociation curve for the ground state of TlH was computed using a relativistic ω–ω coupling formalism. The relativistic effects represented by the Dirac equation were introduced using effective potentials generated from atomic Dirac–Fock wave functions using a generalization of the improved effective potential formulation of Christiansen, Lee, and Pitzer. The multiconfiguration SCF treatment used is a generalization of the two-component molecular spinor formalism of Lee, Ermler, and Pitzer. Using a five configuration wave function we were able to obtain approximately 85% of the experimental dissociation energy. Our computations indicate that the bond is principally sigma in form, despite the large spin–orbit splitting in atomic thallium. Furthermore the bond appears to be slightly ionic (Tl+H−) with about 0.3 extra electron charge on the hydrogen.