A Si-Ge interatomic potential was used to calculate the energy difference between strained and unstrained Ge layers on Si(001) substrates as a function of the number of layers . From this we estimate the critical thickness for dislocation nucleation to be less than 12 layers . The embedded atom method was used to construct embedding functions and pair interactions for bulk Ni and NiSi2. This approach was then used to calculate the energy of the NiSi2/Si (111) interface from which we find that the interface interplanar separation in the Type B case is less than that for Type A.