Surfaces and surface energies in ionic crystals

The stmctures of ionic solids may be accounted for quite accurately by the use of a eottlombie interaetion potential between neighbouring ion pairs together with a suitable ion-core repulsion. 

This procedure can be checked against experimental values which are obtained from the energy to cleave single crystals along specific directions. The agreement is good (see Table 7.2), and since it is of a general nature, the method could even be extended to the elemental semiconductors. 

Oxide r (cation) - -r (airion) (A) Young s modulus (GPa) a calculated (Jm-2) 

The experimental result for MgO from cleavage studies is 7 = 1.30Jm 2. 

---