Structure and low-temperature behaviour of Tlsub(0.82)V5Ssub(4.36)Sesub(3.64)

Msub(r)=849.51, C2/m, a=17.841 (4), b=3.383 (1), c=8.741 (3) A, β=104.88 (2)0, V=509.88 A3, Z=2, Dsub(x)=5.532 g cm-3, Mo Kα, lambda=0.7093 A, μ=299.91 cm-1, F(000)=750, T=295 K, R=0.037 for 842 unique reflections. The structure is built of distorted vanadium chalcogen octahedra connected by face and edge sharing. Owing to the three dimensional framework large quasi-rectangular channels are built in which the T1 atoms are inserted. Magnetic measurements were performed on a crystalline powder sample in the temperature range 74-290 K. The measured susceptibility obeys a Curie-Weiss law with a term for the temperature-independent paramagnetism (TIP). No ordering of the magnetic moments was observed down to the lowest temperatures. A slight discontinuity appears in the susceptibility versus temperature curve around 170 K. This may be due to a phase transition. Differential thermal analysis (DTA) at low temperatures shows an endothermic peak at 168 (2) K. (orig.)