Analysis of electron density changes for two-component spinor and application of spin-orbit density functional theory with relativistic effective core potentials

Abstract

Spin-orbit effects affect the electronic structure of a given system, which can change the molecular spectroscopic constants such as bond lengths, bond dissociation energies and harmonic vibrational frequencies. To understand nature of these spin-orbit effects on molecular properties, we should analyze how orbitals and charge distribution in bonding are changed by spin-orbit interactions. In the present work, we extend the concept of the natural atomic orbitals given by F. Weinhold et al. to natural atomic spinors for relativistic two-component spinors and implement the natural population analysis method for two-component spinors in the Kramers` restricted Hartree-Fock program. And spin-orbit density functional theory method implemented in NWChem program package has been employed with the shape-consistent relativistic effective core potentials to calculate the spectroscopic constants (bond lengths, frequencies and dissociation energies) and estimate spin-orbit effects for 6th(Tl~At)- and 7th(113~117)-row element monohydrides. The spin-orbit effects on the spectroscopic constants from the SO-DFT calculations are in good agreement with previous two-component CCSD(T) results. Calculated spectroscopic constants with the hybrid functionals are in excellent overall agreement with empirical measures. In addition bond lengths, harmonic vibrational frequencies and dissociation energies of TlAt and (113)(117) are calculated at the CCSD(T) and SO-DFT levels of theory. Spin-orbit effects of the bond contraction in group 13 elements and the bond elongation in the group 17 elements almost cancel out for $R_e$ of TlAt and (113)(117). Electron correlations and spin-orbit effects are almost additive in the TlAt molecule, but the non-additivity is quite pronounced for the (113)(117) molecule. Geometries of group 17 fluorides $EF_3$(E= I, At, and element 117) were calculated at the SO-DFT level using relativistic effective core potentials with spin-orbit terms. The influence of s...