Electric center of gravity of overlap charge distribution in impurity-doped ionic crystals

The electric center of gravity (ECG) of the first-neighbor or second-neighbor overlap charge distribution in several alkali-halide crystals doped with monovalent impurity ions is calculated including its dependence on the internuclear distance. The Madelung potentials at this ECG due to the point charges on the normal lattice sites are computed except the contributions from the overlapping ions nearest to the ECG, in order to exclude the two-body potentials. These Madelung potentials are used in the calculation of the three-body potentials in the Ra-Abarenkov-Antonova model.