Lead chalcogenide halides

Fig. 33. Structure relationships and coordinations of lead chalcogenide halides a, Pb4SeBr, b, PbjSjI c, PbvSjBrio. (Redrawn from B. Krebs,. Z. Anorg. Allg. Chem. 396, 137 (1973), Figs. 1 2, and 3, pp. 141, 147, and 148.)...

It was found that the region of formation of the chalcogenide halides depends on the pH, the solvent concentration, and the ratios of the initial components in the charge. Temperature and pressure have practically no influence on the phase formation in these systems (285). The use of bromine (283) and SeBr2 as the solvent leads to a different mechanism, having different kinetics of formation and different growth-forms of the crystals (285). 

Basically, when analysing the band structures, the equivalent observations apply to typical solid state compounds like thallium halides and lead chalcogenides. In studies on the origin of distortion in a-PbO, it was found that the classical theory of hybridization of the lead 6s and 6p orbitals is incorrect and that the lone pair is the result of the lead-oxygen interaction [44]. It was also noted... 

Polymorphic transformations into the structure with Ac > 8 were observed in cesium halides [71-74] atfollowing pressures CsCl 65, CsBr 53, Csl 39 GPa besides, Csl at P > 200 GPa undergoes a smooth second-order transition into a hep structure with Ac = 12. Very peculiar transitions were observed in samarium chalcogenides SmX under high pressures the electron transition Sm(II) Sm(III) takes place with a sharp isomorphic decrease in the lattice parameters. Further compression leads to the transformation of the NaCl CsCl type. Values of pressures at the isomorphic (Pitr) and polymorphic (Pptr) transitions according to [75, 76] are following ... 

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