Ab-initio investigation on the phase stabilities of Au-M Alloys (M = Na, K, Rb and Cs)

Abstract

Ab initio calculations were performed to investigate the structural stability, mechanical, and thermodynamic properties of all intermetallic compounds in the different formulas Au5M, Au2M, AuM, and AuM2 (M = Na, K, Rb, and Cs) in order to clarify their existence and stability in the alkali metal gold binary systems Au-M at 0 K. Several suggested structures and suspect compounds (Au2Cs, AuCs2), which were never reported, were also investigated. The results show that: (i), the compounds Au5Na and Au5Cs in Cu5Ca (hP6), and AuK in CsCl (cP2), are energetically, mechanically and dynamically stable in the suggested structures, respectively. (ii), the compound AuNa in NiAs (hP4) and the proposed compounds Au2Cs in AlB2 (hP3), and AuCs2 in MoSi2 (tI6), are mechanically and dynamically stable in the suggested structures, but are energetically stable close to 0 K, respectively. (iii), the compounds AuK2 in Al2Cu (tI12), Au2Rb in AlB2 (hP3), and AuRb2 in MoSi2 (tI6), are energetically and mechanically stable, but are dynamically unstable in the considered structures, respectively.