Four-Dimensional Incommensurately Modulated Structure of Thulium Polyphosphate

Abstract

Single crystal of rare-earth polyphosphate Tm(PO 3 ) 3 has been grown under high temperature molten-salt method and structurally characterized by single crystal X-ray diffraction analysis. Using the four-dimensional superspace formalism for aperiodic structures, we performed the crystal structure refinement of Tm(PO 3 ) 3 as (3+1)-dimensional incommensurately modulated structure with monoclinic superspace group C2/c(0, 0.358, 0)s0 and a = 14.0620 (12) Å, b = 6.6612 (6) Å, c = 10.0191 (9) Å, β = 127.6043 (9) , R = 0.048 and ωR = 0.050. The structure features infinite chains of corner-sharing PO 4 tetrahedra which are affected by positional modulation running along the b-axis. The final structure model was reasonable and did not show any unusual features.