Crystal structure and X-Ray spectroscopic properties of R.E.2Ni12P5 compounds

Abstract

We have studied experimentally and theoretically the electronic structure and x-ray absorption spectrum at the R.E.L3 - edge and x-ray emission spectra of Ni and P in the R.E.2Ni12P5 compounds. Crystal structure of the ternary phosphate Ce2Ni12P5 has been refined using X-ray powder diffraction pattern of the single phase sample with the same nominal composition, and the isotopic structure as for earlier known La2Ni12P5-type has been proved: space group P21/m, formula units Z = 2, lattice parameters are a = 1.07809(2) nm, b = 0.36869(1) nm, c = 1.31490(3) nm, b = 107.776(4), residual R-values are RI = 0.0681, RP = 0.0442 , RwP = 0.0603. The theoretical calculations have been carried out by means of the ab initio fully-relativistic spinpolarized Dirac linear muffin-tin orbital method. The calculations show good agreement with the experimental measurements. R.E.LIII - absorption spectra in ternary R.E.2Ni12P5 compounds were obtained at 78K and 300K using a tube spectrometer equipped with an RKD-01 co-ordinate detector. The mixed valence state of Ce and Eu was obtained in the Ce2Ni12P5 and Eu2Ni12P5 compounds.