For both terminations, the charge of the atoms inside the slabs matches the charge of the respective atoms in the bulk phase, i.e., 0.5 e for Cu and -1.0 e for O atoms, respectively. In the bulk as well as inside the slabs, each Cu atom is coordinated with two O atoms, while each O atom is coordinated with four Cu atoms. This indicates that on average 0.25 e is transferred The results above raise the following questions: