ON THE EQUILIBRIUM SEGREGATION OF INTERACTING IMPURITY ATOMS TOWARDS (100) METAL-SURFACES .1. THEORETICAL CONSIDERATIONS INCLUDING 1ST-NEIGHBOR AND 2ND-NEIGHBOR INTERACTIONS

Experiments on the segregation of foreign atoms towards single crystal surfaces usually show long-range-order phenomena and/or strong deviations from the Gibbs-McLean behavior both indicating the presence and importance of interactions between the segregating atoms. Model calculations of segregation bulk isosteres for interacting impurity atoms segregating towards (100) metal surfaces are therefore presented based on an extended Ising model using the Monte Carlo method. Interactions between nearest and next-nearest neighbors are considered and bulk isosteres given for a number of combinations of values thereof. In a paper to follow the results of these calculations are to be applied to existing experiments and values for certain interaction enthalpies deduced.