Current experiments suggest that mechanical properties of thin films are different at thicknesses less than 100 nm.In this study, embedded atom method computer simulations are used to examine the differences in strengthening mechanisms at the nano scale.The simulation shows the mechanisms responsible for the differences in hardness with varying sample thicknesses from 12.8, 8, 6, and 4 nm.The simulation results show that as film thickness decreases the hardness of the film increases.Simulations were performed in single crystal films as well as model tricristals in order to study the effects of the grain boundaries.Tricrystalline films emitted dislocations at a lower pressure than single crystals.