All-electron Dirac—Fock—Roothaan calculations on lead oxide

Abstract All-electron (relativistic) Dirac—Fock—Roothaan calculations on the ground state of PbO have been performed. The spectroscopic constants r e (equilibrium bond length),ω e (harmonic frequency) and D e (dissociation energy) have been evaluated and compared to the (nonrelativistic) Hartree—Fock calculations and the experimental data. An extended basis set has been used in almost uncontracted form and the quality of the wavefunction is expected to be near to the Dirac—Fock and the Hartree—Fock limits. We find a 1% relativistic contraction of r e and a 10% variation in the relativistic computation of ω e . The calculated r e and ω e are comparable to the experimental data. The computed D e is about one third of the experimental value; use of density functionals yields the remaining two thirds, thus confirming a large correlation effect.