Cu ejection and sputtering by Ar ions have been studied in the specific case of 5 KeV Ar impinging the (100), (110) and (111) surfaces using the binary collision lattice simulation code COSIPO. The influence of various parameters in treating the binary collisions has been studied. On the basis of these studied the feasibility of binary collision lattice simulations in connection with sputtering is discussed. The effect of interaction potential on sputtering is studied by using two different potential functions for the ion-atom and atom-atom interaction potentials. The strengths of the potentials have been changed by using various screening lengths and cut-offs. To model electronic stopping both frictional and impact parameter dependent electronic losses are used. It is found that the angular distributions of the sputtered atoms depend mainly on the atom-atom interaction potential. The iron-atom potential and the electronic stopping have only minor effects. The yield, however, depends markedly on the inelastic energy losses and the ion-atom potential. The sensitivity of the sputtering yield on the potentials and on the parameters in treating the binary collisions as well as the influence of the simultaneous collisions depend critically on the strength of the potential. Calculations show that the dependence on these factors is weak if the strengths of the potentials are such that the experimental yield are achieved. Several combinations of the interaction potentials and inelastic losses give good agreement with either experimental yields or angular distributions of sputtered particles. However, a combination exists that reproduces all the experimental results.