Paulingʹs electrostatic rule for partially covalent/partially ionic crystals Original Research Article

Second Paulingʹs rule, known as the electrostatic rule, has been reformulated with regard to partial net charges in covalent–ionic crystals. For more uniform treatment, an idea of atomic ionicity coefficients (AIC) related to the respective bond ionicities (BI) is introduced. The proposed definitions are consistent with crystal-chemistry principles. Examples are presented, showing how the reformulated Paulingʹs rule works for chosen compounds. Some other possibilities of applications of the model are also discussed. In particular, for the chosen crystals, the net charges of the ions have been calculated from a knowledge of the ionicities of the respective bonds and the BIs have been estimated from the ionic charges. A case concerning structures with non-equivalent anions is also discussed.