Determination of local geometries around tellurium in TeO{sub 2}-Nb{sub 2}O{sub 5} and TeO{sub 2}-Al{sub 2}O{sub 3} oxide glasses by XANES and EXAFS: Investigation of electronic properties of evidenced oxygen clusters by ab initio calculations
Journal Article
·
· Journal of Solid State Chemistry
- Institut de Chimie de la Matiere Condensee de Bordeaux, Pessac (France); and others
The origin of the high nonlinear optical response in tellurite glasses is tentatively elucidated from a detailed structural investigation of typical glasses existing in the TeO{sub 2}-Al{sub 2}O{sub 3} and TeO{sub 2}-Nb{sub 2}O{sub 5} systems joined to a study of their electronic properties through ab initio calculations. As the proportions of Al{sub 2}O{sub 3} or Nb{sub 2}O{sub 5} increase, the TeO{sub 4} trigonal bipyramids are progressively transformed into a TeO{sub 3+1} asymetric polyhedron, the geometry of which is actually very close to the TeO{sub 3} trigonal pyramids already found in some crystal structures, e.g., in ZnTeO{sub 3}. Ab initio calculations have been performed on TeO{sub 4} and TeO{sub 3} clusters. The highest occupied molecular orbital is of antibonding type and combines 5s AO of tellurium and 2p AO of oxygens. The energy difference between these orbitals and the next vacant molecular orbital is lower for the TeO{sub 4} entity than for the TeO{sub 3} cluster. This result is consistent with a higher polarizability of the TeO{sub 4} entity and accordingly with the higher nonlinear index coefficient n{sub 2} of the richest tellurium glasses.
- OSTI ID:
- 478803
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 2 Vol. 126; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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