Monte Carlo simulation of segregation in ceramic thin films

A Monte Carlo exchange technique is used to study segregation in thin ceramic films with application to MgO/MnO. The approach is not restricted to the dilute limit. Surface concentrations as a function of temperature and film composition are determined directly from the simulations. For all compositions studied (Mn(chi)Mg(1-chi)O, 0 < or = chi < or = 1) the (001) surface is Mn(2+) rich; the occupancy of sites by Mn(2+) decreases rapidly with depth. The ratio of the number of Mn(2+) to Mg(2+) ions at the surface decreases as a function of temperature. The calculated enthalpies of segregation of Mn(2+) for the thin film are strongly dependent on the total Mn(2+) concentration at small Mn(2+) concentrations, with the enthalpy of segregation varying by a factor of two with surface coverage.