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Single-crystal X-ray diffraction has shown that (HoS)1.23NbS2 is a misfit layer compound built of alternate double layers of HoS, approximately a {001} slice of NaCl-type HoS, and sandwiches of NbS2 with niobium in trigonal prisms of sulphur like niobium in 2HNbS2. The unit cell dimensions of the HoS subsystem are a1 = 5.396(1) A, b1 = 5.661(1) A, c1 = 22.195(8) A, β1 = 89.81(2)°, space group F2, Z = 8. The NbS2 lattice with unit cell dimensions a2 = 3.312(1) A, b 2 = 5.661(1) A , c2 = 11.125(7) A, β2 = 86.99(3)°, space group C2, Z = 2 shows twinning, the twin plane being (001). Corresponding a and b axes in the layers of the two subsystems are parallel, while the c axes diverge slightly. The two subsystems have a common ( b∗, c∗ ) reciprocal lattice plane which corresponds in real space to a common projection along [100]. Refinements were performed of the subsystem reflections (Okl excluded) and the common Okl reflections to fix the origin of one subsystem with respect to the other. The HoS distances in the HoS double layer are 2.743(4), 2.754(4), 2.765(4), 2.83(1) and 2.95(1) A; holmium is also coordinated to one or two sulphur atoms of NbS2 (the coordination varies because of the incommensurateness along [100]). The shortest distance is 2.72 A for coordination with one sulphur atom (two other sulphur atoms at distances of 3.18 A) and 2.86 A for coordination with two sulphur atoms of NbS2, holmium atoms in rows parallel to [100] lying in between rows of sulphur atoms of NbS2 sandwiches. The Ho-S distances point to Ho(III). The Nb-S distances are 2.453(8) A (4X) and 2.472(8) A (2X). |
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