Structure determination, electronic and optical properties of rubidium holmium polyphosphate RbHo(PO3)4

Structural, optical, and electronic properties of a new alkali metal-rare earth polyphosphate, RbHo(PO3)4, have been investigated by means of single-crystal X-ray diffraction, power X-ray diffraction, elemental analysis, and spectral measurement. RbHo(PO3)4 crystallizes in the monoclinic with space group P21/n and Z = 4. It is described as a three-dimensional (3D) architecture built up of PO4 double spiral chains and HoO8 polyhedra by corner-sharing. The 11-coordinated rubidium atoms are located in infinite tunnels. Additionally, in order to gain further insight into the relationship between property and structure of RbHo(PO3)4, theoretical calculation based on the density functional theory (DFT) was performed using the total-energy code CASTEP.

► Single-crystal and powder sample of rubidium holmium polyphosphate RbHo(PO3)4 were syntheisized.
► Structure was determined from single-crystal X-ray diffraction.
► Structure is characterized by PO4 double spiral chains, HoO8, and RbO11 polyhedra.
► Crystal RbHo(PO3)4 is an indirect band-gap insulator.
► Powder sample RbHo(PO3)4 exhibits broad emission in the blue–green light region.