Prediction of Madelung Constants

Madelung constants of both simple and complex salts can be reduced to a common scale by taking the nearest-neighbor distance as the unit distance and then dividing by half the sum of the squares of the charges of all the atoms in the stoichiometric unit. These ``reduced Madelung constants,'' α, can be predicted within a few percent by the relation α=1.89—1/m, where m is the harmonic mean coordination number. Madelung constants have been calculated for LaOCl, YOF, ReO3, and several perovskite structures for comparison with the predictions.