Change of short-range order with temperature and composition in liquid GexSe1−x as shown by density measurements
1976; Elsevier BV; Volume: 22; Issue: 2 Linguagem: Inglês
10.1016/0022-3093(76)90059-4
ISSN1873-4812
Autores Tópico(s)Solid-state spectroscopy and crystallography
ResumoDensity measurements were performed on melts of the binary chalcogenide system GexSe1−x (0 ⩽ x ⩽ 0.5) up to 1000°C. The isotherm of molar volumes Vm at 750°C shows a relative maximum near GeSe2. Molar volumes of the system behave linearly between GeSe and Se at 1000°C. Vm's of melts between x = 0.30 and x = 0.35 decrease at high temperatures on heating. The anomalous density behaviour of the melts clearly shows a change of short-range order from a less to a more densely packed structure, caused by the development of a pσ-bonding system. Within the composition range 0 ⩽ x ⩽ 13 the short-range order at lower temperatures is determined mainly by GeSe42 tetrahedra linked directly corner-to-corner or via Se atoms. At higher temperatures pσ bonds arise more and more, even in melts rich in selenium. Within the composition range 13 ⩽ x ⩽ 0.5 the short-range order is mainly determined by a distorted octahedral configuration, even at lower temperatures. From the short-range orders of melts and from crystalline structures of GeSe2 and GeSe, the tendency of glass formation from the melt is discussed in detail.
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