Novel correlation of Schottky constants with lattice energies for II-VI and I-VII compounds

Correlations of computed Schottky constants (KS=[V''Zn][VS..]) with structural and thermodynamic properties showed linear dependences of log KS on the lattice energies for the Zn-, Cd-, Hg-, Mg-, and Sr-chalcogenides and for the Na- and K-halides. These findings suggest a basic relation between the Schottky constants and the lattice energies for these families of compounds from different parts of the Periodic Table, namely, ΔHT,Lo=-(2.303nRT log KS)+2.303nRmb+2.303nRTib. ΔHT,Lo is the experimental (Born-Haber) lattice energy (enthalpy), n is a constant approximately equal to the formal valence (charge) of the material, mb and ib are the slope and intercept, respectively, of the intercept b (of the log KS versus ΔHLo linear relation) versus the reciprocal temperature. The results of this work also provide an empirical correlation between the Gibbs free energy of vacancy formation and the lattice energy. - Graphical abstract: For the Zn-chalcogenides, the quantities n and Ie are 2.007 and 650.3 kcal (2722 kJ), respectively. For the other groups of compounds, they are approximately equal to the formal valences and ionization energies of the metals: Log KS∼-(2.303nRT)-1 (0.99ΔHoT,L-Ie).