Twinned single crystal structure of Li₄P₂S₆

Abstract

Abstract Yellow needles-like single crystals of Li 4 P 2 S 6 were obtained serendipitously during the preparation of Li 7 P 3 S 10 O. The twinned crystal structure of Li 4 P 2 S 6 was determined from single-crystal X-ray diffraction data [w R ( F 2 ) = 0.069, 716 reflections, 40 variables]. Li 4 P 2 S 6 crystallizes in the trigonal system, space group P 3 ‾ m 1 $P\overline{3}m1$ (N° 164), a = 10.5042(8) Å, c = 6.5837(6) Å, V = 629.11(9) Å 3 and Z = 2. The lithium octahedra form a [Li 4 S 6 ] 8− honeycomb-like structure within which diphosphate units are located. The comparison of our crystal structure to those of P 6 3 / mcm -, P 3 ‾ 1 m $P\overline{3}1m$ -, and P 321-Li 4 P 2 S 6 demonstrated group-subgroup relationships and associated the disorder or order of the phosphorus atoms within the identical [Li 4 S 6 ] 8− 3d-frameworks to the choice of the unit cell (the subcell with a ∼ 6.07 Å vs. the supercell with a ∼ 10.5 Å).