The equation of state of polyamorphic germania glass: A two-domain description of the viscoelastic response

Smith, K. H.; Shero, E.; Chizmeshya, Andrew; Wolf, George H.

doi:10.1063/1.469122

Cited by 130 publications

(103 citation statements)

References 39 publications

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“…The equation of state (EOS) of GeO 2 has been reported by different authors, either on the basis of simulations [119] or from empirical models based on simple structural arguments [132]. In the latter, Smith and co-workers have shown that a two state function, taking into account the effect of the tetrahedral and octahedral character at low and high pressures, is able to describe the experimental equation of state at 300 K, whereas molecular dynamics simulations only succeed in simulating the EOS in the low pressure range.…”

Section: Equation Of Statementioning

confidence: 99%

The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

232

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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Section: Equation Of Statementioning

confidence: 99%

The structure of amorphous, crystalline and liquid GeO₂

Micoulaut

Cormier

Henderson

2006

J. Phys.: Condens. Matter

232

252

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“…This lies well above the observed crystallineamorphous transition pressure, which takes place at 16 GPa. However, we must recognize that the two-state EOS does not correspond to a fully relaxed material [Smith et al, 1995]. To estimate the order of magnitude of the correction which might be involved if the volume relaxation associated with the A1 coordination change occurred at lower pressure, we used the "high-temperature liquid" (~2100 K) points from Boslough et al…”

Section: Thermodynamics Of Anorthite At High Pressure Thermodynamics mentioning

confidence: 99%

High‐pressure behavior of anorthite: Compression and amorphization

Daniel¹,

Gillet²,

McMillan³

et al. 1997

J. Geophys. Res.

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Abstract. We present the results of a detailed study of the high-pressure behavior of anorthite (CaA12Si208) between ambient pressure and 30 GPa under static conditions, using in situ Raman spectroscopy and e_ner•[y-dispersive X ray diffraction. On increasing pressure under hydrostatic conditions, the P1-I1 transition occurs first at 2.6 GPa. At 10 GPa, a reversible polymorphic transition is observed which transforms the Ii polymorph into a phase of higher symmetry. With further pressure increase, large changes occur in the Raman and X ray spectra between 14 and 16 GPa, premonitory to the onset of pressure-induced amorphization. Above 16 GPa, anorthite is fully amorphous. However, only samples pressurized to above 22 GPa remain amorphous on recovery to ambient conditions. The high-pressure behavior of anorthite is highly sensitive to deviatoric stresses. Under less hydrostatic conditions, the 10-GPa transition described above occurs below 9 GPa, amorphization begins below 11.2 GPa, and samples decompressed from peak pressures as low as 17 GPa are fully amorphous. We have also carried out a thermodynamic analysis of the pressure-induced amorphization of anorthite, using a two state model for the equation of state (EOS) of CaA12Si20 8 glass in order to account for the increase in A1 coordination. With this EOS, we calculate that the free energies of the crystalline and amorphous materials are equal at about 30 GPa, or slightly lower when effects of structural relaxation in the glass are taken into account, well above the observed crystalline-amorphous transition at 16 GPa.

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“…Although compression measured by Smith et al 24 is greater under hydrostatic loading ͑HL͒, the trend in the data is the same. The bulk and longitudinal wave velocities of vitreous GeO 2 under hydrostatic loading increase slowly with increasing pressure when the pressure is below 4 GPa ͑Fig.…”

Section: A Vitreous Geo 2 Response To Planar Impactmentioning

confidence: 52%

“…Therefore, we conclude that the phase transition to rutile phase in vitreous GeO 2 starts at ϳ4 GPa and is completed in the pressure range of 14 to 16 GPa. Durben and Wolf 16 and Smith et al 24 also inferred that the four-to sixfold GeO 2 transition also occurred between 5.6 and 13 GPa under quasistatic loading.…”

Section: A Vitreous Geo 2 Response To Planar Impactmentioning

confidence: 99%

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Effect of phase change on shock wave attenuation in GeO2

Liu

Ahrens

Brar

2002

Journal of Applied Physics

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Stress-wave profiles in vitreous GeO 2 induced by planar and spherical projectile impact were measured using piezoresistance gauges in the 4 to 18 GPa shock pressure range. The planar experiments demonstrate the response of vitreous GeO 2 . This response can be divided into three regimes: ͑1͒ An elastic shock regime with ramp 4 GPa Hugoniot elastic limit ͑HEL͒ precursor. Shock propagation velocity decreases from an initial longitudinal elastic wave speed of 3.5 to 2.8 km/s at 4 GPa. ͑2͒ A transition wave regime where the ramp wave is superimposed on the precursor with an additional amplitude of 0 to 2 GPa followed by a sharp increase in shock pressure achieving peak loading pressures of 8 to 14 GPa. Above 4 GPa the ramp wave velocity decreases to a value below 2.5 km/s ͑the speed of the bulk wave, at the HEL͒. ͑3͒ A shock wave achieving the final shock state forms when peak pressure is Ͼ6 GPa specified by linear shock-particle velocity relation D ϭ0.917ϩ1.71 u ͑km/s͒ over the 6 -40 GPa range for an initial density of 3.655 g/cm 3 . The Hugoniots of GeO 2 and SiO 2 , both initially vitreous, are found to be virtually coincident if pressure in SiO 2 is calculated by multiplying the GeO 2 pressure by the ratio of the initial densities of vitreous GeO 2 to fused SiO 2 . The volume axes are translated by aligning the specific volumes for onset and completion of the four-to six-fold coordination phase change. Although only limited spherical impactor spherically diverging shock experiments were conducted, our present results demonstrate ͑1͒ The supported elastic shock in fused SiO 2 decays less rapidly than a linear elastic wave when elastic wave stress amplitude is higher than 4 GPa. A supported elastic precursor in vitreous GeO 2 decays faster with radius than a linear elastic wave; ͑2͒ in GeO 2 ͑vitreous͒ unsupported shock waves decay with peak pressure in a phase transition range ͑4 -15 GPa͒ with propagation radius ͑r͒ as ϰr Ϫ3.35 .

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The equation of state of polyamorphic germania glass: A two-domain description of the viscoelastic response

Cited by 130 publications

References 39 publications

The structure of amorphous, crystalline and liquid GeO₂

The structure of amorphous, crystalline and liquid GeO₂

High‐pressure behavior of anorthite: Compression and amorphization

Effect of phase change on shock wave attenuation in GeO2

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The equation of state of polyamorphic germania glass: A two-domain description of the viscoelastic response

Cited by 130 publications

References 39 publications

The structure of amorphous, crystalline and liquid GeO2

The structure of amorphous, crystalline and liquid GeO2

High‐pressure behavior of anorthite: Compression and amorphization

Effect of phase change on shock wave attenuation in GeO2

Contact Info

Product

Resources

About

The structure of amorphous, crystalline and liquid GeO₂

The structure of amorphous, crystalline and liquid GeO₂