On the theory of anisotropy of crystalline surface tension

Abstract Application of fundamental geometrical and statistical mechanical principles to the terrace ledge kink (TLK) model of crystalline surfaces leads to a two-parameter theory of the anisotropy of surface tension (specific free energy). The contribution to ledge free energy due to the entropy associated with kinks and the effect of neighboring ledges in restricting the kink density as the ledge spacing decreases are calculated by treating each ledge as a cooperative chain. The results show clearly the importance of the kink entropy contribution to ledge free energy. Examples of the predicted anisotropy of surface tension are given for copper. The predicted variations in surface tension are such that rounded areas can appear on the equilibrium form. A critical underpressure is predicted to be necessary to force ledges together on an evaporating crystal.