First-principles study of phase stability of bcc XZn (X=Cu, Ag, and Au) alloys

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Abstract

First-principles density-functional theory is used to study the phase stability/instability and anomalies in the formation of the high-temperature bcc phases of XZn (X = Cu, Ag, and Au) alloys. Although from perhaps a naive point of view, their properties are expected to monotonically depend on the noble-metal (X) column position in the periodic table, this is not the case. For example, the middle-column AgZn alloy has a lower bcc order-disorder (critical) temperature than the CuZn and AuZn alloys above and below in the column. It is shown that this and other nonmonotonic behaviors can be explained in terms of a competition between atomic-size effects and X-atom d-orbital spatial extent. For example, charge-density studies and pair-potential modeling of XZn alloys show that the effective Ag-Zn bond is significantly weaker than either the Cu-Zn or Au-Zn bond at their respective equilibrium lattice constants. We find that an increased atomic-core size effect initially weakens the X-Zn b
Original languageEnglish
Pages (from-to)113601
JournalPhysical Review M
DOIs
StatePublished - Nov 5 2018

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