<i>Ab initio</i>study of spin-orbit coupling effects on the low-lying excited states of NiO

Abstract

We show the results of ab initio embedded cluster calculations of the ground state and low-lying excited states of the (001) surface and bulk of NiO including the spin-orbit coupling effects. The calculations are performed by the COLUMBUS package using the combination of the relativistic effective core potentials and the spin-orbit operators. These effects result in the splitting of the $d\text{\ensuremath{-}}d$ excited states. The fine structure of the $3{d}^{8}$ levels of the ${\mathrm{Ni}}^{2+}$ ion in NiO bulk and its (001) surface is resolved yielding good agreement with experimentally observed second-harmonic and optical absorption spectra. In addition, we discuss the transition electric-dipole moments, which can be used for a quantitative comparison with the experimentally determined optical intensities as well as for the exploration of various ultrafast all-optical spin-switching scenarios.