All-electron Dirac–Fock–Roothaan calculations for the ThO molecule

Accurate all-electron Dirac–Fock–Roothaan calculations were performed for the 1Σ+ ground state of ThO using Gaussian basis sets of Th (24s20p16d12f)/[19s15p12d5f] and O (10s6p1d)/[7s4p1d]. The relativistic effects in ThO were found to slightly extend the bond length re, to increase the dissociation energy De, and to decrease the harmonic frequency ωe.