Potential of X-Ray Diffractometry in Structure Identification of Holmium Polysulfides

Holmium polysulfide crystals: Structure, shape and composition

“…for atoms of an appropriate multiplicity of positions within a certain unit cell and a space group, provided by the correct account for interdependence of s.o.f., temperature parameters and absorption. A new performance of structural investigation for the series of crystals has been planned due to the obtained evidence that most of the holmium polysulfide crystals had only monoclinic symmetry [12]. Besides the selection of crystals of different shapes and sizes and of appropriate quality, we had to examine thoroughly the convergence in intensities for equivalent reflections to fulfil monoclinic cell conversion and try finding superreflections for a tetragonal crystal.…”

“…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 formation of another phase was not established by this method, perhaps, owing to significant minority of the same [12]. The details of the experiment will be published elsewhere.…”

“…In the monoclinic polysulfide, the layers with disulfide pairs are disposed in the plane (1 01) (see Fig. 1), which, therefore, predetermine formation of the most developed facets of crystals, analogously [11,12]. The four-fold axis is absent for disulfide pairs in the monoclinic structure, therefore the formation of square developed pinacoid for monoclinic crystals is, most likely, incidental, especially since sides of this "square" are not exactly equal, if the sizes of crystals I, II and V are taken into account ( Table 2).…”

“…The structural analysis of a series of different shape crystals, with- out structure refinement, pointed to simultaneous crystallization of these two phases under the same conditions. At the same time, it was established by a special experiment that the monoclinic phase crystallized mainly, irrespective of crystallization conditions [12]. The structure and composition refinement for the series of holmium polysulfide crystals of different habits has been carried out by X-ray single crystal method, and both the influence of growth conditions on chemical composition and the principles of formation of different crystal shapes are discussed in the present work.…”