REFINEMENT OF THE ZrNi0.8P2-x CRYSTAL STRUCTURE
Journal Title: Праці Наукового товариства ім. Шевченка - Year 2017, Vol 48, Issue
Abstract
Crystal structure of the earlier known ternary phosphide with approximate composition ZrNi0.75P2 was refined by X-ray powder diffraction method and atomic positional parameters were calculated that leading to the exact composition described by a formula ZrNi0.8P2-х (х = 0.2): space group P4/nmm, HfCuSi2-type structure, lattice parameters а = 0.35806(2) nm, с = 0.88711(5) nm, residual values RI = 0.0417, RP = 0.0390, RwP = 0.0526. Starting materials for the samples preparation were powders of zirconium, nickel, and red phosphorus, all with the stated purity not less than 99.95 mass %. Mixtures of the constituents in the stoichiometric ratio were pressed into pellets. The pellets were placed within evacuated fused silica tubes which were slowly heated to 1070 K (200 K per day), kept at this temperature over 100 h, and then cooled to room temperature by shutting off the furnace. The sintered samples were grounded, pressed again into pellets, and then were annealed within evacuated fused silica tubes at 1 070 K during 1000–1200 h, and quenched in cold water without breaking the tubes. All samples have been studied by X-ray phase and structural analysis using DRON-3M diffractometer (Cu Kα-radiation). For all calculations the WinCSD software has been used. Crystal structure of the ternary phosphide ZrNi0.8P2-х (х = 0.2) was found to be isotypic with the earlier known ternary arsenide ZrNi0.75As2 (HfCuSi2-type structure, defective derivative from the tetragonal CaBe2Ge2 structure) with the partial occupation by Ni and P1 atoms of the crystallographic positions 2b and 2a, respectively. Interatomic distances in the structure of the ZrNi0.8P2-х phosphide are nearly the same as the respective sum of the atomic radii of the components. Distances reducing being observed between atoms of metals and phosphorus dNi–P2 = 0.2248(5) nm, and dZr–P2 = 0.2725(3) nm are less than 5 % of the respective sum of the atomic radii values, so can indicate predominantly metallic type of bonding between metals and phosphorus atoms. Peculiarities of the ZrNi0.8P2-х structure and its relationship with the CaBe2Ge2-type structure have been discussed.
Authors and Affiliations
Olga ZHAK
Keywords
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