Lattice energies of cubic alkaline-earth oxides. Affinity of oxygen for two electrons

The lattice energies of these crystals were calculated from equations based on the Born model and containing terms accounting for van der Waals interactions. The results were, in kilocalories per mole: MgO, −905; CaO, −815; SrO, −767; BaO, −736. These lattice energies, when combined with appropriate thermochemical data, yielded 149 ± 8 kcal/mole for the increase in enthalpy of the reaction of atomic oxygen with two electrons. This value is less than most values previously computed for this process. The decreased value is attributed to the higher, more accurate compressibilities used in evaluating the lattice energies of these oxides.