Crystal structure of Ag₇Ca₂ - a new intermetallic structure type

Single crystals of Ag₇Ca₂ were grown and examined without the application of mechanical stress. The crystal structure was solved by single-crystal X-ray diffraction. Ag₇Ca₂ is orthorhombic, space group Cmcm, a = 9.478(2) A ̊, b = 5.525(1) A ̊, c = 14.079(2) A ̊, Z = 4, R = 0.034, with a simple new structure type containing Kagomé nets of silver atoms, surrounded by hexagonal and triangular nets of silver and calcium atoms. These layers are then stacked as in hexagonal close packing. Predicted mechanical properties are discussed briefly. The c-axis conductivity of Ag₇Ca₂, measured as a function of temperature on a single crystal, approaches that of silver metal.