Lattice energy from point-charge model

Kubaschewski (1972) collected and compared the enthalpies of formation of complex oxides from binary oxides. He did not offer any systematic correlation of these enthalpies with structural properties. Hoppe (1966,1970a, b, 1975) developed the MAPLE concept (Madelung part of lattice energy) as a tool to guide the structural interpretation of bonding in complex oxides and halides. It requires as input parameters the unit cell of a compound and positions of all atoms, and it treats the crystal as an ionic array of point charges. If crystal structure determinations have been properly done, MAPLE calculations for a complex compound are within 2% (sometimes larger, sometimes smaller) of the MAPLE values of the binary (parent) compounds. Therefore, purely ionic-model calculations are not suflftciently sensitive to correlate quantitatively with the relatively small enthalpies of solid-state complexation. 

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