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In this review, we make a survey of the structure studies for the chalcogen elements and several chalcogenides in liquid, amorphous and nanosized state by using X-ray absorption fine structure (XAFS). The chalcogen elements have hierarchic structures; the chain structure constructed with the strong covalent bond as a primary structure, and the weaker interaction between chains as a secondary one. Existence of these two kinds of interactions induces exotic behaviors in the liquid, amorphous and nanosized state of the chalcogen and chalcogenides. XAFS is a powerful structure analysis technique for multi-element systems and the disordered materials, so it is suitable for the study of such as liquid, amorphous and nanosized mixtures. In section 2, the structures for the liquid state are discussed, which show the interesting semiconductor-metal transition depending on their temperatures and components. In section 3, the structure for the amorphous states are discussed. Especially, some of chalcogens and chalcogenides present the photostructural change, which is important industrial application. In section 4, the structures of nanosized state, nanoparticles and isolated chain confined into the narrow channel, are discussed. The studies of the nanoparticle and the isolated chain reveal the alternative role between the intrachain covalent bonds and the interchain interaction. [ABSTRACT FROM AUTHOR]

The structure of crystal GeCu2Te3 was investigated by X-ray absorption fine structure (XAFS) measurement. We found that the Ge-Te interatomic distances obtained from XAFS are larger than those obtained from X-ray diffraction, and the Cu-Te distances are smaller. The averaged Ge-Te and Cu-Te distances obtained from XAFS are almost equal to the corresponding interatomic distances in amorphous GeCu2Te3. Therefore both crystal and amorphous GeCu2Te3 seem to be built up of the same local configurations of GeTe4 and CuTe4 tetrahedrons. This would be the reason why the phase change in GeCu2Te3 occurs very fast. [ABSTRACT FROM AUTHOR]