Misfit effects in adhesion calculations

Abstract

The work of adhesion of bimaterial interfaces is commonly computed using quantum mechanical methods in which the two materials are strained into coherency. There is no relaxation of the coherency by the formation of an array of interfacial misfit dislocations, contrary to what is commonly observed for essentially all systems other than very thin films. In this paper, we investigate the errors introduced into the work of adhesion associated with the assumption of coherency. Series of atomistic simulations in two and three dimensions are performed using a simple Lennard-Jones-type model potential. We demonstrate that the assumption of coherency introduces errors that increase rapidly with misfit (for small misfit) and can easily be of the order of several tens of percent. We trace the source of these errors to the neglect of the elastic fields of misfit dislocations and to the variation in the number of bonds per unit interfacial area with misfit when coherency is assumed. Suggestions are made to minimize and/or correct for this error.