Monte Carlo simulation of segregation in ceramic thin films: Comparison of the MgO/MnO {1Â 0Â 0} and {2Â 1Â 0} surfaces

A Monte Carlo exchange technique is used to study segregation in thin ceramic films with application to the Mg1−xMnxO {1 0 0} and {2 1 0} surfaces. Unlike previous atomistic simulations of segregation the method is not restricted to the dilute limit. For all compositions studied (0⩽x⩽1), the surface is Mn2+ rich; the occupancy of sites by Mn2+ decreases rapidly with depth. The ratio of the number of Mn2+ to Mg2+ ions at the surface decreases as a function of temperature. Segregation is greater at {2 1 0} than {0 0 1} surface, consistent with the relative difference in surface energies. Surface concentrations as a function of temperature and film composition are determined directly from the simulations. The calculated enthalpies of segregation are strongly dependent on the surface coverage, particularly for low Mn2+ mole fractions.