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Holmium polysulfide crystals: Structure, shape and composition

“…All of them were twins with an identical twinning law with respect to the (101) plane, differing only by a twin component weight value (the second, main, component is determined by difference from one). The HoS 2−x compositions were identical for all the crystals, within the error 1.5σ max = 0.01, and were equal to HoS 1.837 (3) , that is closest to rational formula Ho 6 S 11 (Z = 4), calculated by the method, suggested by us in [11]. The idea behind the calculation is the sulfur atom by atom removal of a unit cell with the maximum composition Ln 24 S 48 known for the light RE polysulfides from the given structural type, till the composition determined in accordance with s.o.f.…”

“…All the crystals investigated (I-V) were found to be analogous in the unit cell parameters and the symmetry with the monoclinic crystal from [11]. All of them were twins with an identical twinning law with respect to the (101) plane, differing only by a twin component weight value (the second, main, component is determined by difference from one).…”

“…For the crystals I, III, V, the experimental data sets were obtained for an independent (according to the symmetry) area, 0 ≤ h ≤ 17; 0 ≤ k ≤ 18; Table 1 Experimental conditions Run no. −17 ≤ l ≤ 17, for the crystal IV in a reverse space hemisphere, whereas for the monoclinic crystal, from [11], the intensity set area was combined-up to θ = 25 • , the data collection was made as for triclinic crystal, and in the area 25 • ≤ θ ≤ 35 • as for a monoclinic crystal. It gave different equivalent reflection sets for estimation of symmetric intensity correlations and crystal quality and a value R int .…”

“…is received. The monoclinic crystal composition of HoS 1.863 (8) was described by the formulae Ho 8 S 15 in [11]. However, studying the P S -T-x diagram of HoS 2.0 -HoS 1.5 system by the tensimetric method showed the holmium polysulfide to have the composition HoS 1.83 (1) .…”

“…The crystal with the tetragonal structure, space group P4/nmm, which represented the "parental" type unit cell metrics [3] (a ≈ a 0 and c ≈ c 0 ≈ 2a 0 ), had a square prism habitus and the composition HoS 1.885 . The crystal of the monoclinic syngony -space group P2 1 /m, with unit cell parameters connected with the "parental" structural type by [1 0 1] ∼ = 4a 0 , [0 1 0] ∼ = 3a 0 , [1 01] ∼ = 2c 0 correlation -appeared like a very thin rectangular plate and had the composition HoS 1.863 [11]. Both the structural types occur in a number of RE polychalcogenide phases [2].…”