Structure determination of CuTh₂(PO₄)₃

Abstract

The crystal structure of CuTh 2 (PO 4 ) 3 , copper dithorium triphosphate, has been solved ab initio from conventional monochromatic X-ray powder diffraction and refined with neutron powder diffraction data. The symmetry is monoclinic, space group C2/c. The heavy-atom positions were found from a Patterson map calculated from integrated intensities extracted by whole-pattern fitting. Successive Fourier syntheses were used to locate the remaining atoms. The Th atoms and PO 4 groups exhibit an arrangement related to that found in the M I Th 2 (PT h ) 3 phases, with large sites in which the monovalent cations are located. In the title compound, these sites are elongated along a and shortened along b so that the Cu + ions, located on inversion centres, are linearly bonded to two phosphate groups with two short Cu-O distances of 1.828 A.