Hydrothermal Synthesis of New Phosphate K2Sc(OH)[PO3(OH)]2, Structure, and Prediction of Variants

Single crystals of new phosphate K2Sc(OH)[PO3(OH)]2 were synthesized under hydrothermal conditions, sp. gr. P21/m, a = 7.6182(15) Å, b = 5.4036(9) Å, c = 10.287(2) Å, β = 96.53(2)°. The structure consists of blocks, which are composed of the central ScO5(ОН) octahedron and five vertex-sharing [РО3(ОН)] tetrahedra, whereas many silicates, phosphates, and germanates contain six such tetrahedra. In the new phosphate, the distortion and imperfection of the blocks lead to their connection, forming ribbons, and prevent them from linking together to form layers, as in the structure of aphthitalite (glaserite) K3Na(SO4)2. The new phosphate was compared with the mineral vitusite Na3Ce0.55La0.45[PO4]3. The structure consisting of corrugated layers, which are generated by repeating the ribbons along the c axis and displacing them along the b axis, and a new framework structure were predicted by topology and symmetry analysis.