Molecular dynamics (MD) study on copper sulfide (Cu_2S) crystal which is subjected to sliding condition is performed. The hexagonal crystal structure of Cu_2S is determined by first-principle calculation, first. Values on the optimized structure are adopted to the construction the potential function which includes three-body term as well as pair term, resembling MoS_2 case. In MD simulations, a Cu_2S crystal undergoes relaxation and compression processes at first, then it is applied shear deformation and is slid on the hexagonal basal plane. The dependency on sliding direction with regard to hexagonal slip system and on sliding velocity is investigated. It is found that layers of Cu_2S slide without retaining their prescribed crystal stacking and shape. Under various temperature conditions, the sliding of the crystal is simulated and the shear resistance (averaged shear stress) shows a certain temperature-dependency, indicating stick-slip motion in some cases.
