Raman spectroscopic study of the pressure-induced coordination change in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">GeO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>glass

Durben, Dan J.; Wolf, George H.

doi:10.1103/physrevb.43.2355

Cited by 151 publications

(120 citation statements)

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“…Up to 6 GP a, Durben and Wolf [84] observe a shift of the main Raman band at ≃ 420 cm −1 to higher frequency with concomitant broadening and loss of intensity. Between 6 and 13 GP a the main Raman band broadens and losses intensity without a shift in frequency.…”

Section: Increasing Pressure and Temperaturementioning

confidence: 96%

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The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

228

256

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Abstract. Germanium dioxide (GeO 2 ) is a chemical analogue of SiO 2 . Furthermore, it is also to some extent a structural analogue, as the low and high-pressure short-range order (tetrahedral and octahedral) is the same. However, a number of differences exist. For example, the GeO 2 phase diagram exhibits a smaller number of polymorphs, and all three GeO 2 phases (crystalline, glass, liquid) have an increased sensitivity to pressure, undergoing pressure induced changes at much lower pressures than their equivalent SiO 2 analogues. In addition, differences exist in GeO 2 glass in the medium range order, resulting in the glass transition temperature of germania being much lower than for silica. This review highlights the structure of amorphous GeO 2 by different experimental (e.g., Raman and NMR spectroscopy, neutron and x-ray diffraction) and theoretical methods (e.g., classical molecular dynamics, ab initio calculations). It also addresses the structure of liquid and crystalline GeO 2 that have received much less attention. Furthermore, we compare and contrast the structural differences between GeO 2 and SiO 2 , as well as, along the GeO 2 − SiO 2 join. It is probably a very timely review as interest in this compound, that can be investigated in the liquid state at relatively low temperatures and pressures, continues to increase.

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Section: Increasing Pressure and Temperaturementioning

confidence: 96%

“…Up to 5 GPa, both Durban and Wolf [84] and Polsky et al [85] suggest that compression of the GeO 2 glass network is taken up be tetrahedral deformation with a smaller decrease in the intertetrahedral angle. In addition, they conclude that there is no increase in intensity of the 520 cm −1 D 2 band.…”

Section: Increasing Pressure and Temperaturementioning

confidence: 99%

The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

228

256

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“…Above 5 GPa, compression takes places mostly through coordination changes with the formation of 5-or 6-fold Ge (5,7,8), accompanied by a rapid increase in density (8)(9)(10). The coordination change is completed at Ϸ12 GPa, above which GeO 2 glass behaves as an octahedral glass with 6-fold Ge coordination (8,11).…”

mentioning

confidence: 99%

“…Because the coordination change with increasing pressure is a general feature for tetrahedral glasses and melts (5,7,8,11,(19)(20)(21), the observed thermal phenomena for GeO 2 glass with different local structures may be applied to other tetrahedral glasses and even melts. A tetrahedrally coordinated glass/melt at low pressures may display a modest thermal effect (e.g., densification) associated with the relaxation in an intermediate range order, but with only a small change in the short-range order.…”

mentioning

confidence: 99%

Distinct thermal behavior of GeO ₂ glass in tetrahedral, intermediate, and octahedral forms

Shen

Liermann

Sinogeikin

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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One fascinating high-pressure behavior of tetrahedral glasses and melts is the local coordination change with increasing pressure, which provides a structural basis for understanding numerous anomalies in their high-pressure properties. Because the coordination change is often not retained upon decompression, studies must be conducted in situ. Previous in situ studies have revealed that the short-range order of tetrahedrally structured glasses and melts changes above a threshold pressure and gradually transforms to an octahedral form with further pressure increase. Here, we report a thermal effect associated with the coordination change at given pressures and show distinct thermal behaviors of GeO2 glass in tetrahedral, octahedral, and their intermediate forms. An unusual thermally induced densification, as large as 16%, was observed on a GeO2 glass at a pressure of 5.5 gigapascal (GPa), based on in situ density and x-ray diffraction measurements at simultaneously high pressures and high temperatures. The large thermal densification at high pressure was found to be associated with the 4-to 6-fold coordination increase. Experiments at other pressures show that the tetrahedral GeO2 glass displayed small thermal densification at 3.3 GPa arising from the relaxation of intermediate range structure, whereas the octahedral glass at 12.3 GPa did not display any detectable thermal effects.amorphous materials ͉ high pressure ͉ thermal densification

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“…That study utilized X-ray absorption data for Ga and both XANES and EXAFS revealed no evidence for a coordination shift for synthesis pressures up to 25 kbar. More recent in-situ studies of coordination have illustrated a pressure-induced coordination shift of Ge at much higher pressures than those investigated here (Durben and Wolf, 1991). For GeO2 glasses, in-situ high-pressure XAS studies have shown a transition from 4-fold to 6-fold coordination at ~ 70 kbar and it has been found to be similar to that occurring in crystalline GeO2 (i.e.…”

Section: Discussionmentioning

confidence: 92%

Pressure-induced coordination change of Ti in silicate glass: a XANES study

et al. 1994

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Abstract. The effect of pressure on titanium coordination in glasses, with composition K2TiSi4Oll, quenched isobarically from liquids equilibrated at high pressure (5, 10, 15, 20, 25, 30 kbar respectively) and T= 1600 ~ C has been investigated by X-ray absorption spectroscopy (XAS). The XANES spectra collected at the Ti K-edge clearly show a variation with pressure that is related to changes in the geometrical environment around the Ti atoms. By comparison with spectra of standard materials, the XANES spectra of the glasses suggest a relatively low average coordination number (near 5) in samples quenched at low pressure and a higher coordination number (near 6) in samples quenched from the highest pressure. The combination of XANES data with density and compressibility measurements supports the idea that a mixture of 6-and lower coordinated (4-and/or 5-coordinated) Ti geometries are present in the 1 bar glass, and an increasing proportion of 6-coordinated Ti occurs in the glasses synthesized at progressively higher pressures.

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Raman spectroscopic study of the pressure-induced coordination change inGeO2glass

Cited by 151 publications

References 70 publications

The structure of amorphous, crystalline and liquid GeO₂

The structure of amorphous, crystalline and liquid GeO₂

Distinct thermal behavior of GeO ₂ glass in tetrahedral, intermediate, and octahedral forms

Pressure-induced coordination change of Ti in silicate glass: a XANES study

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Raman spectroscopic study of the pressure-induced coordination change inGeO2glass

Cited by 151 publications

References 70 publications

The structure of amorphous, crystalline and liquid GeO2

The structure of amorphous, crystalline and liquid GeO2

Distinct thermal behavior of GeO 2 glass in tetrahedral, intermediate, and octahedral forms

Pressure-induced coordination change of Ti in silicate glass: a XANES study

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The structure of amorphous, crystalline and liquid GeO₂

The structure of amorphous, crystalline and liquid GeO₂

Distinct thermal behavior of GeO ₂ glass in tetrahedral, intermediate, and octahedral forms