Charge localization in diatomic ions investigated with a dipole driven approach. II. Interplay with the spin–orbit coupling and polarization models, test for (KrXe)+

Recently, we have proposed a method for the construction of charge-localized (approximately diabatic) basis sets of mixed rare-gas dimer cations based on the point-charge approximation of the dimer dipole moment matrix and applied it to the (NeAr)+ molecular ion [M. Ćosićová et al., J. Chem. Phys. 163, 044303 (2025)]. In the present paper, the method is extended to be applicable to heavier rare gases, and a specific application to (KrXe)+ is presented. The extension of the original method mainly consists in considering (a) relativistic effects (the spin–orbit coupling, in particular) in the electronic cloud of the studied system and (b) the polarizability of rare-gas atoms, both extensions being important for heavy rare gases. High-level ab initio calculations using multi-reference configuration interaction methods have been performed to obtain accurate inputs to the proposed charge-localization scheme and compared with available literature data.