Structure-property relationship in cubic Zr7Ru6+хGa17-x (0 ≤ x ≤ 2.0): disorder, electrical transport and bonding

The new ternary berthollide Zr7Ru6+xGa17-x (0 ≤ x ≤ 2.0) has been synthesized by arc melting stoichiometric amounts of the elements. The homogeneity ranges at 870 K of the phases have been examined using powder x-ray diffraction and energy-dispersive X-ray analysis. Zr7Ru6Ga17 crystallizes in a new cubic structure-type (Pearson symbol cF120, space group Fm3 ̅m no. 225, a = 12.409(1) Å, Z = 4) extending the family of closely-related cubic structures described by the Pearson symbols cF116–120. The crystal structure of Zr7Ru6Ga17 can be regarded as a deficient superstructure polyhedral variant of CaF2 [1]. Density-functional electronic structure calculations performed for an ordered structural approximant uncover pronounced features near the Fermi level, including several van Hove singularities, indicative of a potential electronic instability. Chemical bonding analysis based on –COHP method reveals that heteroatomic Zr-Ga and Ru-Ga contacts dominate the bonding landscape, with zirconium showing an unexpectedly strong covalent contribution despite its minority fraction. Complementary physical measurements demonstrate a characteristic type of transport and thermodynamic behavior that is directly influenced by the structural disorder and the peculiar electronic structure. The combination of a new cubic architecture, Fermi-level singularities and unconventional bonding motifs places Zr7Ru6+xGa17-x as a promising platform for exploring structure-property correlations in Ga-rich intermetallics and expands the chemistry of the cF120 family.