Structural evolution of rutile-type and CaCl 2 -type germanium dioxide at high pressure

Haines, J.; Léger, Jean‐Michel; Chateau, C.; Pereira, Altaïr Soria

doi:10.1007/s002690000092

Cited by 86 publications

(75 citation statements)

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“…The high pressure orthorhombic phase has the CaCl 2 -type structure (space group Pnnm, Z ¼ 2). The lattice parameters at 36 GPa, for example, a is slightly smaller than that reported for the same high pressure phase (14.90(9) cm 3 /mol at 36 GPa) [33] obtained by pressurizing rutile-type GeO 2 at quasi-hydrostatic (methanol -ethanol -water pressure medium) conditions.…”

Section: Geo 2 Polymorphismmentioning

confidence: 69%

See 1 more Smart Citation

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

Prakapenka

Shen

Dubrovinsky

et al. 2004

Journal of Physics and Chemistry of Solids

122

129

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Section: Geo 2 Polymorphismmentioning

confidence: 69%

“…6). However, no intermediate phase, analogous to quartz-II for SiO 2 , has been detected for GeO 2 in our and other studies [33]. This monoclinic phase was observed to at least 52 GPa and remains stable on decompression to ambient pressure.…”

Section: Geo 2 Polymorphismmentioning

confidence: 69%

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

Prakapenka

Shen

Dubrovinsky

et al. 2004

Journal of Physics and Chemistry of Solids

122

129

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“…3(b), at the transition pressure, the lattice parameter a corresponding to the rutile phase splits in a and b from the CaCl 2 -type structure, while the behavior of the c parameter with respect to pressure remains almost constant. This transition has been also observed from XRD measurements and DFT calculations in other rutile fluorides and oxides such as MgF 2 , 6 SiO 2 , 37 and GeO 2 , 38 to name a few. (6) fluorite (8) rutile ( Upon further compression in a pressure range between 10 and 14 GPa, new peaks appear in the diffraction patterns, corresponding to a phase coexistence and characterized by a crystal volume contraction of 8%, within this pressure range.…”

Section: A Xrd Studiesmentioning

confidence: 71%

Pressure-induced phase-transition sequence in CoF2: An experimental and first-principles study on the crystal, vibrational, and electronic properties

et al. 2013

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We report a complete structural study of CoF 2 under pressure. Its crystal structure and vibrational and electronic properties have been studied both theoretically and experimentally using first-principles density functional theory (DFT) methods, x-ray diffraction, x-ray absorption at Co K-edge experiments, Raman spectroscopy, and optical absorption in the 0-80 GPa range. We have determined the structural phase-transition sequence in CoF 2 and corresponding transition pressures. The results are similar to other transition-metal difluorides such as FeF 2 but different to ZnF 2 and MgF 2 , despite that the Co 2+ size (ionic radius) is similar to Zn 2+ and Mg 2+ . We found that the complete phase-transition sequence is tetragonal rutile (P 4 2 /mnm) → CaCl 2 type (orthorhombic P nnm) → distorted PdF 2 (orthorhombic P bca) + PdF 2 (cubic P a3) in coexistence → fluorite (cubic F m3m) → cotunnite (orthorhombic P nma). It was observed that the structural phase transition to the fluorite at 15 GPa involves a drastic change of coordination from sixfold octahedral to eightfold cubic with important modifications in the vibrational and electronic properties. We show that the stabilization of this high-pressure cubic phase is possible under nonhydrostatic conditions since ideal hydrostaticity would stabilize the distorted-fluorite structure (tetragonal I 4/mmm) instead. Although the first rutile → CaCl 2 -type second-order phase transition is subtle by Raman spectroscopy, it was possible to define it through the broadening of the E g Raman mode which is split in the CaCl 2 -type phase. First-principles DFT calculations are in fair agreement with the experimental Raman mode frequencies, thus providing an accurate description for all vibrational modes and elastic properties of CoF 2 as a function of pressure.

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“…This indicates the formation of Si − O − Ge bonds but also the existence of an important number of Si − O − Si and Ge − O − Ge linkages. According to these authors, the Si/Ge ordering is likely non-ideal, which supports a random distribution of SiO 4 and GeO 4 tetrahedra (see comment above regarding 17 O NMR). In a Molecular Dynamics simulation of a 50GeO 2 − 50SiO 2 glass [106], a large fraction of Ge − O − Si bonds were found, as well as, Ge−O −Ge and Si−O −Si linkages.…”

Section: Raman Spectroscopymentioning

confidence: 83%

“…Indeed, this peak corresponds to Si and/or Ge neighbors and both its position and its intensity vary upon Si/Ge substitution. 17 O multiple quantum NMR spectra on GeO 2 − SiO 2 binary glasses which show peaks for all three types of bridging oxygens (Ge − O − Ge, Ge − O − Si, Si − O − Si), in proportions at least roughly consistent with random mixing of the tetrahedral cations [103].…”

Section: Exafs and X-ray Scatteringmentioning

confidence: 99%

The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

227

252

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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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Structural evolution of rutile-type and CaCl 2 -type germanium dioxide at high pressure

Cited by 86 publications

References 0 publications

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

Pressure-induced phase-transition sequence in CoF2: An experimental and first-principles study on the crystal, vibrational, and electronic properties

The structure of amorphous, crystalline and liquid GeO₂

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Structural evolution of rutile-type and CaCl 2 -type germanium dioxide at high pressure

Cited by 86 publications

References 0 publications

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

High pressure induced phase transformation of SiO2 and GeO2: difference and similarity

Pressure-induced phase-transition sequence in CoF2: An experimental and first-principles study on the crystal, vibrational, and electronic properties

The structure of amorphous, crystalline and liquid GeO2

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Product

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The structure of amorphous, crystalline and liquid GeO₂