Investigating Gold Intermetallics Featuring Disordered Networks



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Intermetallic compounds consist of two or more metallic elements that form an ordered structure in a defined stoichiometric ratio. They may possess desirable properties, such as catalysis, superconductivity, and super hardness, with various industrial applications in fields like energy and aerospace. Accordingly, this drives the increased demand to discover new intermetallic compounds. Gold-based intermetallics, in particular, form diverse and complex crystal structures owing to gold's relativistic effects. In this work, systematic exploration was performed in the RE-Au-Si (RE=Y, La) and Na-Au-Cd systems, revealing four new gold-based intermetallic phases with nominal compositions Y(Au0.28Si0.72)2, La(Au0.24Si0.76)2, Na(Au0.51Cd0.49)2, and Na(Au0.9Cd0.1)2. RE-Au-Si phases were arc melted, while Na-Au-Cd phases were reacted in sealed Ta containers at 600°C, followed by annealing at 400°C. The resulting crystal structures were determined via single crystal x-ray diffraction. Y(Au0.28Si0.72)2 and La(Au0.24Si0.76)2 are isotypic and crystallize in the AlB2-type structure, while Na(Au0.51Cd0.49)2 crystallizes in the MgZn2-type structure and Na(Au0.9Cd0.1)2 in the MgCu2-type structure. All four phases feature disordered networks with Au/Si or Au/Cd sites respectively. Le Bail refinement of powder x-ray diffractograms indicates the presence of the product phases, with minor impurities. Density of states calculations reveal metallic behavior in all four phases. These results support that complex intermetallic compounds are significantly influenced by diverse constituents and gold's relativistic effects.