THIS INFORMATION IS OBSOLETE AND IS PROVIDED ONLY FOR ITS HISTORICAL VALUE

222. MADE: Coulombic Lattice Energy of an Ionic Crystal by A. B. Blake, Department of Chemistry, University of Hull, Hull, England A knowledge of the lattice energies of crystals containing complex ions is useful in the estimation of bond energies and charge distributions from thermochemical data. This program calculates the electrostatic ("Madelung") part of the cohesive energy of an ionic crystal of any structure and complexity by the method of Bertaut. The net electrostatic cohesive energy of a crystal is changed if the point-charge ions are replaced by equivalent spherical-distributions of charge density s(r). The (negative) energy per mole is then where n is the number of formula units per unit cell. WT is the total electrostatic energy of the periodic charge distribution, per unit cell, and is given by where V is the unit-cell volume; F'(hkl) (the 'electric structure factor') is defined as where qj is the charge on the ion whose fractional coordinates in the unit cell are xj,uj,zj; F(S) is the Fourier transform of the normalised charge-density function s(r); and S (hkl) is the distance of the point h, k, l from the origin of the reciprocal lattice, given by . Here O(a,~)*, O(b,~)*, and O(c,~)* are the edges of the reciprocal cell. The sum over h, k, l is to include all positive and negative integral values of these indices except h=k=1=0; however, it converges fairly rapidly and may be terminated by setting a maximum to the value of S. Wp is a correction for the overlap of the individual ionic charge-distributions s(r), and is zero if these are chosen so that s(r) = 0 for r > ro, where 2ro, The program provides four alternative choices for the form of s(r). These are uniform, linear, parabolic, and Gaussian. FORTRAN Lines of Code: 715 Recommended Citation: A. B. Blake, QCPE 11, 222 (1972).