An Examination of Verwey's Model for the Lattice Structure of the Free Surface of Alkali Halide Crystals

The Verwey model for the free surface structure of alkali halide crystals at 0° K. has been used to estimate the effect of surface distortion on the surface energy of these crystals. It appears that the contributions from distortion are considerably larger than previously reported. In the case of some lithium salts the corrected surface energy becomes negative; the mechanical stability of the solid is considered in the light of this. Several aspects of the Verwey model have been examined. These include the effect of various repulsive potentials and forms of distortion.