Direct exchange and interaction of 3d impurities on the (001) surface of iron

We present a detailed ab-initio study of direct exchange and interaction pr ocesses of 3d atoms on the Fe(0 0 1) surface. The calculations art: based o n local density functional theory and apply a KKB-Green's function method f or impurities on surfaces. For practically all 3d transition metal impuriti es on Fe(0 0 1) we find a strong tendency for a direct exchange mechanism i nto the first surface layer. The early 3d impurities V, Cr and Mn strongly repel each other on neighbouring positions within the first layer, while Ni and Cu atoms show a moderate repulsion. The ab-initio results are in good agreement with STM studies for Cr/Fe(0 0 1) by the NIST group and present v aluable predictions for all 3d/Fe(0 0 1) systems. (C) 1999 Elsevier Science B.V. All rights reserved.