The Role of Coordinate Covalence in Nonmolecular Solids

This paper describes a coordinated polymeric model of nonmolecular solids which pictures each atom as joined to each neighbor of opposite kind by a polar covalent bond. The covalent bond energy is taken as the geometric mean of the two homonuclear single bond energies, adjusted for bond length. The ionic bond energy is determined using a modified Born-Mayer equation. The weighting coefficient for the ionic contribution is the ratio of partial charge to oxidation number. The total atomization energy is the weighted sum of covalent and ionic contributions. Calculated and experimental values agree well for more than 100 solid halides and chalcides. The coordinated polymeric model is superior to the simple ionic model in its applicability over a complete polarity range.