By using this material as a prototype brittle solid, it was shown that the energy which was associated with newly created ledge surfaces and dislocations at a crack tip could be obtained by means of first-principles calculations. These results were incorporated into a continuum theory for the critical loading of cracks by assuming an evanescent force law for the surface effects. The results indicated that the inclusion of surface ledge effects could change the value of the critical load by up to 20%.

Y.M.Juan, Y.Sun, E.Kaxiras: Philosophical Magazine Letters, 1996, 73[5], 233-40