The method of increments, which is a wavefunction-based correlation method for solids, is extended to metals. Whereas the Hartree-Fock energy is calculated in the infinite periodic solid, the correlation energy of the solid is expanded in terms of localised orbitals or a group of localised orbitals. For the metals the so-called correlation energy increments are determined in finite, properly embedded fragments of the metal. First applications to the ground-state properties of solid mercury yield very good agreement with experiment[1, 2, 3]. In this paper we present the extension of the method to solid barium. Whereas the metallic character in mercury is due to the hybridisation of the 6s electrons with the 6p orbitals, in barium it is due to the hybridisation with the 5d orbitals. Due to a proper embedding scheme we can to model the electronic structure of bulk barium and In the case of barium we have to use multi-reference methods for the incremental treatment of the correlation energy.

@inproceedings{PaulusAnIM,
title={An Incremental Method for the Calculation of the Electron Correlation Energy in Metals},
author={Beate Paulus and Alexander V Mitin}
}