Materials Properties of Ultra-Incompressible Re2P

In situ high-pressure X-ray powder diffraction measurements on Re 2 P up to 37.0 GPa at ambient temperature in diamond-anvil cells were carried out at two different synchrotron facilities (ESRF and DESY). The compressibility of Re 2 P ( Pnma, no. 62, a = 5.5464(17), b = 2.9421(8), c = 10.0483(35) Å, V = 163.97(9) Å 3, Z = 4, R p = 0.1008, wR p = 0.1341 at ambient conditions) was investigated and resulted in a bulk modulus of B 0 = 320(10) GPa after fitting the experimental p – V data to a second- and third-order Birch–Murnaghan equation of state. In addition, the determined bulk modulus is compared to values obtained from an Eulerian strain versus normalized stress plot with values ranging form 315(7) to 321(15) GPa. These experimental findings are confirmed by density functional theory (DFT)-calculations ranking Re 2 P among ultra-incompressible materials. However, the Vickers hardness of a high-pressure sintered Re 2 P–Re x C y composite material in the asymptotic hardness region was found to be of only 13(2) GPa. Electrical conductivity measurements indicate that metallic Re 2 P exhibits Pauli-paramagnetism. Analysis of temperature-dependent in situ X-ray diffractometry reveals an approximately isotropic expansion of the lattice parameters with a thermal expansion coefficient of (α( V ) = 28.5–32.8(2)·10 –6 K –1 ).