Surface alloys of Pd and Cu via atomistic modeling

Atomistic modeling using parameter-dependent approximate methods has become a useful tool for the understanding of the basic features and mechanisms of complex surface processes. In most cases, however, the inadequate transferability of the input parameters results in their becoming specific to each particular application. Unlike other methods, the BFS method for alloys is a quantum approximate formalism with the advantage that all the needed parameters, computed via first-principles calculations or from experimental input, are transferable, in the sense that both surface and bulk problems are dealt with using the same set of parameters with no loss in accuracy. This characteristic of the BFS method is highlighted in the study of Cu-Pd surface alloys presented in this work, focusing on the deposition of Pd on Cu(100) and Cu(110), and Cu on Pd(110), showing excellent agreement with experiment in all cases: (a) Pd/Cu(100) exhibits a c(2 x 2) structure for low Pd coverages, (b) Pd/Cu(110) shows the formation of Pd-Cu chains, resulting into a Cu3Pd one-layer surface alloy and (c) Cu/Pd(110) displays the formation of mono-atomic linear chains oriented in the [110] direction for low Cu coverage. This work shows that such a wide range of results can be obtained from the same set of parameters, thus enhancing the predictive power and reliability of this technique. (C) 2001 Elsevier Science B.V. All rights reserved.