MISFIT EFFECTS IN ADHESION CALCULATIONS

The work of adhesion of bimaterial interfaces is commonly computed usi ng quantum mechanical methods in which the two materials are strained into coherency. There is no relaxation of the coherency by the formati on of an array of interfacial misfit dislocations, contrary to what is commonly observed for essentially all systems ether than very thin fi lms. In this paper, we investigate the errors introduced into the work of adhesion associated with the assumption of coherency. Series of at omistic simulations in two and three dimensions are performed using a simple Lennard-Jones-type model potential. We demonstrate that the ass umption of coherency introduces errors that increase rapidly with misf it (for small misfit) and can easily be of the order of several tens o f percent. We trace the source of these errors to the neglect of the e lastic fields of misfit dislocations and to the variation in the numbe r of bonds per unit interfacial area with misfit when coherency is ass umed. Suggestions are made to minimize and/or correct for this error.