Molecular dynamics investigation on the role of sliding interfaces and friction in the formation of amorphous phases

Molecular dynamics simulations have been employed to gain deeper insight into the microscopic dynamics of crystalline solids when mechanical forces are applied. In particular, the study focuses on the atomic scale mechanisms involved in the shear-induced relative sliding of atomic planes. Two different systems have been investigated, namely a smooth phase boundary between crystalline Ni and Zr metal lattices and a crystalline bulk region of the NiZr₂ intermetallic compound. In both cases, a conventional tight-binding potential was used to reproduce the interatomic forces. Numerical calculations demonstrate that the application of shear stresses determines the deformation of the crystal and the formation of a sliding interface. A density decrease, and a corresponding increase in the average free volume available to atomic species, is observed near the sliding interface. Chemical disordering processes take place at the interface as a result of frictional forces operating during the shear-induced sliding. The generation of chemical disorder is accompanied by the accumulation of structural disorder that determines the formation of an amorphous domain at the interfacial region in both the binary and the intermetallic systems.