New implementation of molecular double point-group symmetry in four-component relativistic Gaussian-type spinors

A new, practical implementation of double-group symmetry to relativistic Gaussian spinors is presented for four-component relativistic molecular calculations. We show that the systematic adaptability to irreducible representations under arbitrary point-group symmetry, as well as Kramers (time-reversal) symmetry, is inherent in the present basis spinors, which possess the analytic structure of Dirac atomic spinors. The implementation of double-group symmetry entails significant computational efficiencies in the relativistic second-order Maller-Plesset perturbation calculation on Au ₂ and the density functional theory (DFT) calculation with the B3LYP functional on octahedral UF₆, in which the highest symmetries used are, respectively, C*_6h and D*_4H. The four-component B3LYP equilibrium geometry of UF₆ is reported.