Problems encountered in calculations of collisional mixing in compounds

Problems encountered in the description of ion-induced compositional changes in non-monatomic solids, on the basis of the binary collision approach (BCA), are reported. The ingredients of a collisional model responsible for eventual ambiguity of computer simulation results are pointed out. The conclusion is made that application of the BCA to ion-induced composition build-up problem can require preliminary parametrization of the collisional model used for a given target composition. Financial support from DGICyT (project PS89-0065), A NATO grant, tile Spanish MAE (in collaboration with Sweden) and a postdoctoral grant to VK from the Spanish MEC are acknowledged.