Molecular dynamics sliding simulations of amorphous Ni, Ni-P and nanocrystalline Ni films

Abstract

Molecular dynamics modeling is used to investigate the sliding feature of different nano-scale specimens: single-crystal nickel evolving from amorphous pure Ni during shear deformation, Ni-P amorphous layer and nanocrystalline nickel. Special attentions are paid to the value of resistance stresses and plastic deformation mechanisms manifested during sliding simulations. The study is performed for considered systems at a temperature of about 300K with narrow acceptable range of temperature fluctuation. It was found that Ni-P amorphous structure is characterized by lowest resistance stresses and smooth sliding provided by the bond-switching mechanism between pairs of atoms due to shear loading. Similar low resistance stress was also observed for an amorphous pure Ni layer, but only at an early stage of sliding before crystallization occurred. The highest shear resistance was confirmed for single-crystal nickel caused by classical deformation mechanisms like stacking fault formation and dislocation movement. Sliding simulations of a nanocrystalline specimen show both, crystal defect driven deformation in the bulk and sliding along quasi-amorphous grain boundaries. In that case the resistance force was between amorphous layer sliding and single crystal sliding, but closer to amorphous layer sliding.