The -2 charge state of V Mg corresponds to the filling of the t 2 state of the Si 4 molecular orbitals with 2 additional electrons (Figure ), which exist in the valence band so that V -2 Mg forms when E F is in the band gap. Similarly, the mainly +2 charge state of V Si corresponds to the depopulation of the t 1u states of the Mg 8 complex (Figure ), which in the neutral charge state is filled with 2 electrons.