Structure and electronic properties of the orthorhombic MoRuP superconductor prepared at high pressure

The orthorhombic superconductor MoRuP (o-MoRuP) was prepared under high pressure, and its structure was refined using the x-ray Rietveld technique. The grayish-black sample of o-MoRuP is a superconductor with T c = 15.5 Kand having space group Pnma and lattice parameters a = 6.03503(16) A, b = 3.85311(8) A, and c = 6.94355(17) A, V = 161.463(7) A. 3 The structure of o-MoRuP is characterized by layers (parallel to the ac plane) of Mo, Ru, and P atoms. Based on the accurately determined crystal structure, the band structure and the density of states (DOS) of o-MoRuP were calculated by a first-principles density-functional method and compared with those of the isostructural superconductor o-ZrRuP (T c =4 K). It is shown that the high T c in o-MoRuP is directly related to the higher level of the DOS at the Fermi level (E F ) and is traced to be predominantly from the Mo 4d orbitals. The calculated values of the DOS at E F are 0.46 and 0.33 states/eV atom for the Mo and Zr analogs, respectively. The electronic bonding in these two crystals is analyzed in terms of the Mulliken effective charge and the bond order values. The bonding in o-MoRuP differs from that in o-ZrRuP in that there is a short (2.44 A) Mo-P bond. The x-ray reference pattern of o-MoRuP prepared using a Rietveld decomposition technique has been submitted to the International Center for Diffraction Data to be included in the Powder Diffraction File.