  Bimetallic alloys have drawn extensive attentions in materials science due to
their widespread applications in electronics, engineering and catalysis. A very
fundamental question of alloy is its surface segregation phenomenon. Many
recent observations have shown that reactive gases or supports may have strong
effects on alloy segregation. However, segregation in water, the most common
solvent and environment, has not received enough attention. In this paper we
give the quantitative descriptions on the surface segregation energies of 23
transition-metal impurities in Cu hosts under the conditions of water
adsorption by performing density functional theory (DFT) calculations. The
general trends in the changes of segregation energies caused by water
adsorption are established. Our results show water adsorption could induce
strong surface segregation tendencies for early and middle transition metals in
Cu alloys. This finding not only prompts us to re-examine the potential effects
of water on bimetallic alloy surfaces, but would be also very helpful as a
guide for the further theoretical and experimental studies in this field.
