Electronic Structure and Thermal Properties of a Cubic Laves Compound NaAg₂ Featuring a [Ag₄]^2- Pyrochlore Network

A sample of the cubic Laves phase (Strukturbericht C-15) NaAg₂ was synthesized by prolonged low-temperature annealing (300°C, 3 months) of elemental sodium and silver. Heat capacity measurements were performed on the resulting polycrystalline sample. The compound was found to exhibit metallic properties and no superconducting transition was observed down to T = 2 K. The crystal structure of the compound hosts a [Ag₄]^2- pyrochlore network. Density functional theory-based ab initio electronic structure calculations were carried out for NaAg₂. Based on these, the contribution of [Ag₄]^2- fragment orbitals, the connection of the electronic band structure to the simple four-orbital nearest-neighbor tight binding model, and the importance of higher-order neighbor interactions are discussed.