Nanoscale alloying: A study in free Cu-Ag bimetallic clusters

Abundance measurements of bimetallic clusters synthesized in gas phase could address the issues of alloying between two metals at nanometer scale. In fact, these studies might be able to answer why some metals do not form good alloy in bulk phase, from an atomic point of view. We report one such investigation between Cu and Ag atoms. Formation of free bimetallic clusters between these two coin metals is investigated up to 7100 amu by synthesizing them in gas phase under completely unperturbed conditions. The results produce evidence of magic combination as proposed in several theoretical calculations. A total of 1465 binary CumAgn nanoclusters could be identified in which many magic compositions appear with higher abundances. Overall, it is observed that Cu and Ag atoms do not mix randomly but preferably surface segregate. The findings validate the structure motif reported in theoretical studies and thereby, depict a natural selectivity in the formation of these nanoscale alloys. Thus, the study contributes in the understanding of fundamental issues involved in alloying between two noble metals. (C) 2013 Elsevier B.V. All rights reserved.