0000000000378754

AUTHOR

Valeria Diella

showing 3 related works from this author

Fe-periclase reactivity at Earth's lower mantle conditions: Ab-initio geochemical modelling

2017

Intrinsic and extrinsic stability of the (Mg, Fe) O solid mixture in the Fe-Mg-Si-O system at high P, T conditions relevant to the Earth's mantle is investigated by the combination of quantum mechanical calculations (Hartree-26 Fock/DFT hybrid scheme), cluster expansion techniques and statistical thermodynamics. Iron in the (Mg, Fe) O binary mixture is assumed to be either in the low spin (LS) or in the high spin (HS) state. Un-mixing at solid state is observed only for the LS condition in the 23-42 GPa pressure range, whereas HS does not give rise to un-mixing. LS (Mg, Fe) O un-mixings are shown to be able to incorporate iron by subsolidus reactions with a reservoir of a virtual bridgmanit…

Subsolidus reaction modellingMgO-FeO binary010504 meteorology & atmospheric sciencesSilicate perovskiteLower mantle geochemical heterogeneitiesAnalytical chemistryAb initioLower mantle geochemical heterogeneities MgO-FeO binary Mixing Gibbs energy Pyrolitic geochemical mode Subsolidus reaction modellingMineralogyengineering.material010502 geochemistry & geophysics01 natural sciencesMantle (geology)Geochemistry and PetrologyMixing Gibbs energy0105 earth and related environmental sciencesPyrolitic geochemical modeSettore GEO/06 - MineralogiaPyrolitic geochemical modelAmbientaleDiamondHartreePartition coefficientengineeringPericlaseMgO-FeO binaryPyrolitic geochemical modelLower mantle geochemical heterogeneitiesSubsolidus reaction modellingMixing Gibbs energyGeologyCluster expansion
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Modelling of thermo-chemical properties over the sub-solidus MgO–FeO binary, as a function of iron spin configuration, composition and temperature

2014

Thermo-chemical properties and T–X phase relations diagram of the (Mg,Fe)O solid solution are modelled using mixing Helmholtz energy, ΔF(T,x)mixing, calculated by quantum mechanical and semi-empirical techniques. The sub-solidus MgO–FeO binary has been explored as a function of composition, with iron either in high-spin (HS) or low-spin (LS) configuration. Only the HS model provides physically sound results at room pressure, yielding a correct trend of cell edge versus composition, whereas LS’s issues are at variance with observations. Mixing Helmholtz energy has been parametrized by the following relationship: ΔF(T,x)mixing = x × y × [U0(T) + U1(T) × (x – y) + U2(T) × (x − y)2]−T × S(x,y)c…

ChemistryDegrees of freedom (physics and chemistry)(MgFe)OThermodynamicsSolidusMixing energyGibbs free energyMixing energy; Ab initio and semi-empirical modelling; (Mg; Fe)Osymbols.namesakeCrystallography(MgFe)O; Ab initio and semi-empirical modelling; Mixing energy; Geochemistry and Petrology; Materials Science (all)Geochemistry and PetrologyPhase (matter)Helmholtz free energysymbolsRelaxation (physics)General Materials ScienceMaterials Science (all)(MgFe)OAb initio and semi-empirical modellingMixing (physics)Solid solutionPhysics and Chemistry of Minerals
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Lower mantle hydrogen partitioning between periclase and perovskite : a quantum chemical modelling

2016

Abstract Partitioning of hydrogen (often referred to as H2O) between periclase (pe) and perovskite (pvk) at lower mantle conditions (24–80 GPa) was investigated using quantum mechanics, equilibrium reaction thermodynamics and by monitoring two H-incorporation models. One of these (MSWV) was based on replacements provided by Mg2+ ↔ 2H+ and Si4+ ↔ 4H+; while the other (MSWA) relied upon substitutions in 2Mg2+ ↔ Al3+ + H+ and Si4+ ↔ Al3+ + H+. H2O partitioning in these phases was considered in the light of homogeneous (Bulk Silicate Earth; pvk: 75%–pe:16% model contents) and heterogeneous (Layered Mantle; pvk:78%–pe:14% modal contents) mantle geochemical models, which were configured for lower…

010504 meteorology & atmospheric sciencesHydrogenpericlaseAnalytical chemistrySocio-culturalechemistry.chemical_elementengineering.material010502 geochemistry & geophysics01 natural sciencesMantle (geology)chemistry.chemical_compoundGeochemistry and PetrologyOrganic chemistryH2O-partitioningperovskiteEquilibrium constant0105 earth and related environmental sciencesChemistryAb-initio calculationslowermantle; H2O-partitioning; periclase; perovskite.SilicatePartition coefficientlower mantleAnhydrousengineeringPericlaseChemical equilibriumlower mantle H2O-partitioning Ab-initio calculations periclase perovskite
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