Adhesion/atomistic friction surface interaction model with application to interfacial fracture and nanofabrication

A novel adhesion/atomistic friction (Ad/AF) surface interaction model has been developed for solid materials interacting through van der Waals dispersive forces. This model was motivated by friction force microscopy data that suggest that in at least some cases a pressure-independent interfacial shear strength can be used to describe molecular-level friction. The Ad/AF model has two elements. Adhesion is defined by a traction–separation relationship, where the key parameters are interfacial strength and the work of adhesion. The second element of the Ad/AF model defines the nature of interfacial shear stress in a way that is consistent with a pressure-independent interfacial shear strength. The model assumes friction acts only when the opposing materials are in contact. The Ad/AF model, which has been implemented within an explicit dynamics finite element code, has been applied to several problems where adhesion and atomistic friction are expected to play an important role. Illustrative results from interfacial fracture and nano-embossing simulations are presented. The fracture simulation shows that the Ad/AF surface interaction model generates a strongly mode-dependent effective interfacial toughness (i.e., depends on the relative level of the applied shear). The nano-embossing simulations indicate that even low levels of adhesion and atomistic friction can have a significant effect on nanofabrication processes.