Diffusion and viscosity of Mg2SiO4 liquid at high pressure from first-principles simulations

Ghosh, Debashri; Karki, Bijaya B.

doi:10.1016/j.gca.2011.05.030

Cited by 46 publications

(45 citation statements)

References 44 publications

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“…Viscosity of silicate melts can be computed from molecular dynamics simulations using the Green‐Kubo relation [ Spera et al ., ; Ghosh and Karki , ] at temperatures that are generally well above experimental conditions. The corresponding viscosities are of the order of 10 −3 –1 Pa·s, i.e., at the lower end of the experimental low viscosity range.…”

Section: Viscositymentioning

confidence: 95%

“…Figure illustrates a scarce case where CMD [ Adjaoud et al ., ] and FPMD [ Ghosh and Karki , ] results for the viscosity of forsterite (Mg 2 SiO 4 ) liquid can be directly compared to laboratory measurements at 0 GPa [ Urbain et al ., ]. At 2500–4000 K, the MD data fall on the VFT extrapolation of experimental results; outside that temperature range, the computed viscosity values follow an Arrhenian behavior, diverging from the VFT extrapolation to lower values.…”

Section: Viscositymentioning

confidence: 99%

“…[] CMD, Adjaoud et al . [] CMD, and Ghosh and Karki [] FPMD. Experimental data with a VFT fit (crosses and the solid curve) [ Urbain et al ., ] are shown for comparison.…”

Section: Viscositymentioning

confidence: 99%

“…The Eyring equation applies more successfully to polymerized than to depolymerized melts [ Tinker et al ., ]. The necessity of greater jump distances for the Eyring equation to hold—moving the fit curve to lower diffusivity in Figure a—has prompted some authors to speculate that in some cases SiO 4 4− units are the actual diffusing species [ Dunn , ; Adjaoud et al ., ; Ghosh and Karki , ].…”

Section: Links Between Transport Propertiesmentioning

confidence: 99%

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Transport properties of silicate melts

Hui

Steinle‐Neumann

2015

Reviews of Geophysics

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A quantitative description of the transport properties, diffusivity, viscosity, electrical, and thermal conductivity, of silicate melts is essential for understanding melting-related petrologic and geodynamic processes. We here provide a systematic overview on the current knowledge of these properties from experiments and molecular dynamics simulations, their dependence on pressure, temperature, and composition, atomistic processes underlying them, and physical models to describe their variations. We further establish phenomenological and physical links between diffusivity, viscosity, and electrical conductivity that are based on structural rearrangement in the melt. Neutral molecules and network-modifying cations with low electric field strength display intrinsic diffusivity, which is controlled by the intrinsic properties (size and valence) of the species. By contrast, oxygen and network formers with high field strength show extrinsic diffusivity, which is more sensitive to extrinsic parameters including temperature (T), pressure (P), and melt composition (X). Similar T-P-X dependence of diffusivity and electrical conductivity and their quantitative relation reveal the role of intrinsically diffusing species in electrical transport, while viscosity is tied to the extrinsically diffusing species in a similar way. However, the differences in the structural role and mobility of various atomic species diminish with increasing temperature and/or pressure: all transport processes are increasingly coupled, eventually converging to a uniform rate and mechanism. Accurate comprehension of interatomic interactions and melt structure is vital to fully accounting for the compositional dependence of transport properties, and simple polymerization parameters such as nonbridging oxygen per tetrahedrally coordinated cation are inadequate.

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Section: Viscositymentioning

confidence: 95%

Section: Viscositymentioning

confidence: 99%

“…[] CMD, Adjaoud et al . [] CMD, and Ghosh and Karki [] FPMD. Experimental data with a VFT fit (crosses and the solid curve) [ Urbain et al ., ] are shown for comparison.…”

Section: Viscositymentioning

confidence: 99%

Section: Links Between Transport Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Transport properties of silicate melts

Hui

Steinle‐Neumann

2015

Reviews of Geophysics

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“…Bouhifd et al, 2004;Chevrel et al, 2014). Additionally, there is no data for depolymerised, low viscosity Fe-rich liquids, and computational methods have only investigated Mg-rich liquid viscosities such as MgSiO 3 (Karki and Stixrude, 2010) and Mg 2 SiO 4 (Ghosh and Karki, 2011). Therefore, experimental determination of high-P physical properties of such Fe-rich liquids is required.…”

Section: Introductionmentioning

confidence: 99%

Viscosity of liquid fayalite up to 9 GPa

Spice

Sanloup

Cochain

et al. 2015

Geochimica et Cosmochimica Acta

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The viscosity of liquid fayalite (Fe 2 SiO 4 ) was determined up to 9.2 GPa and 1850°C using in situ falling sphere viscometry and X-ray radiography imaging. The viscosity of liquid fayalite was found to decrease both along the melting curve and an isotherm, therefore temperature is thought to have little effect on liquid fayalite viscosity at high pressure. The results are in contrast with previous studies on depolymerised silicate melts which found viscosity to increase with pressure. In accordance with recent in situ structural measurements on liquid fayalite, the viscosity decrease is likely a result of the increase in Fe-O coordination with pressure. The results show that liquid silicate viscosities need to be considered on an individual basis and can be strongly dependent on the melt structure and composition. This has important implications for models of planetary differentiation. In particular, terrestrial bodies with high Fe contents and reducing mantle conditions are likely to have had very mobile melts at depth.

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Experimental Constraints on Ferropericlase (Mg, Fe)O Melt Viscosity Up to 70 GPa

Deng

Lee

2017

Geophysical Research Letters

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During Earth's accretion, Earth's mantle is expected to have been a magma ocean due to large impacts. As such, properties of molten mantle materials are key to understanding Earth's thermochemical evolution. However, due to experimental challenges, transport properties at lower mantle pressures, particularly viscosity, are poorly constrained for mantle melts. In this study, we use quenched dendritic textures to estimate melt viscosities at high pressures for (Mg, Fe)O ferropericlase, one of the major components of the mantle. We find that the viscosity of (Mg, Fe)O melt near liquidus temperatures is 10 À3-10 À2 Pa s over the pressure range of 3-70 GPa, which is~1-2 orders of magnitude lower than previous results for Si-rich melts at similar conditions. This may have implications for magma ocean cooling and thermochemical evolution of the mantle.

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Diffusion and viscosity of Mg2SiO4 liquid at high pressure from first-principles simulations

Cited by 46 publications

References 44 publications

Transport properties of silicate melts

Transport properties of silicate melts

Viscosity of liquid fayalite up to 9 GPa

Experimental Constraints on Ferropericlase (Mg, Fe)O Melt Viscosity Up to 70 GPa

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