Search results for " Ab-initio calculation"

showing 3 items of 3 documents

Trace element fractionation through halite crystallisation: Geochemical mechanisms and environmental implications

2019

Halite is an important mineral for industry, agriculture and food production. It crystallises after water evaporation, while the progressive growth of dissolved metal ions in brines is occurring. Then, halite exploitation may provide the delivery of metal ions in the environment and the mechanism of this trace element accumulation should be studied. In this work we investigate the distribution of lanthanides and Y (hereafter named Rare Earth Elements, REE), Zr and Hf between crystallising halite and brines in the Dead Sea as geochemical tools for recognising the mechanism of metal ion removal from brines and accumulation in halite. Halite forms cubic crystals where octahedral planes sometim…

Environmental Engineering010504 meteorology & atmospheric sciencesEvaporiteChemistryMetal ions in aqueous solutionInorganic chemistryDead Sea Zr-Hf decoupling Ab-initio calculation REE Environmental pollution De-icing saltTrace elementEnvironmental pollution010501 environmental sciencesengineering.material01 natural sciencesPollutionMetalCrystalvisual_artengineeringvisual_art.visual_art_mediumEnvironmental ChemistryHaliteWaste Management and DisposalDissolution0105 earth and related environmental sciencesScience of The Total Environment
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Magnetic field-induced alignment of molecular rotor-shaped cyclophanes

2010

Molecular pinwheels consisting of dipolar substituted cyclophanes in solution can function as free microscopic rotors in the presence of a homogeneous static magnetic field B and a circularly polarized electric field E rotating on a plane containing B. Owing to the high magnetic anisotropy of [26](1,2,3,4,5,6)cyclophane and [36](1,2,3,4,5,6)cyclophane biased by strong ring currents, ∼1 in 105 molecules are expected to align with the C6 symmetry axis perpendicular to a magnetic field of 21 T. The magnetic-field-controlled alignment of rotor-shaped cyclophanes is insignificantly affected by nonpolar solvents, for example, toluene.

ChemistryRotor-shaped cyclophanes; molecular engines; magnetic field-controlled molecular alignment; dipolar rotors in circularly polarized electric field; ab-initio calculations; solvent effectsMagnetostaticsMolecular physicsSymmetry (physics)Magnetic fieldDipolechemistry.chemical_compoundMagnetic anisotropyNuclear magnetic resonanceElectric fieldPerpendicularGeneral Materials SciencePhysical and Theoretical ChemistryCyclophane
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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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