Structural instability and superconductivity in the solid solution SrNi sub(2)(P sub(1-x)Ge sub(x)) sub(2)

The solid solution SrNi sub(2)(P sub(1-x)Ge sub(x)) sub(2) with ThCr sub(2)Si sub(2)-type structure has been synthesized over the whole composition range by high-temperature solid state reactions. Structure investigations were performed using X-ray diffraction (XRD) methods. In addition, in situ temperature-dependent powder XRD measurements down to 10K were carried out for two SrNi sub(2)(P sub(1-x)Ge sub(x)) sub(2) samples with x=0.110(3) and 0.212(3), which indicate a temperature-induced collapse of the structure of the first compound around 200K. For both samples, superconductivity was detected above 1.8K by magnetic, resistivity, and heat capacity measurements (T sub(C)3.0 and 2.4K, respectively). The crystal chemistry and the chemical bonding in the superconducting compounds are discussed in terms of linear muffin-tin orbital (LMTO) band structure calculations including density of states (DOS), crystal orbital Hamilton populations (COHPs), and a topological analysis using the electron localization function (ELF).