Quaternary thorium transition metal pnictide oxides: ThCu1-xPO, ThCuAsO, and Th2Ni3-xP3O

The new compounds ThCu1-xPO and ThCuAsO with ZrCuSiAs-type structure were prepared in well crystallized form by chemical vapor transport reactions. Th2Ni3-xP3O with a new structure type was obtained by reaction of ThO2 with the other elemental components in an alumina crucible at high temperatures. The crystal structures of the three compounds were determined from single-crystal X-ray data. ThCu1-xPO: P4/nmm, a = 389.43(4), c 828.3(1) pm, R = 0.024 for 13 variable parameters and 338 structure factors: ThCuAsO: P4/ nmm, a = 396.14(5), c = 844.0(1) pm, R = 0.028 (13 variables and 379 F values); Th2Ni3-xP3O: P4/nmm, a = 394.62(4), c = 1723.2(3) pm, R 0.018 (27 variables and 374 F values). The refinement of the occupancy parameters revealed significant deviations from the ideal values for the transition metal sites for two compounds resulting in the exact compositions ThCu0.938(4)PO and Th2Ni2.45(1)P3O. Magnetic susceptibility measurements indicate Pauli paramagnetism for ThCu1-xPO. The crystal structures of these compounds are closely related. They belong to a large family of tetragonal structures of which the ThCr2Si2- and the PbFCl-type structures are well known examples. (orig.)