Incorporation of water in iron-free ringwoodite: A first-principles study
-
Marc Blanchard,
,
Etienne Balan
Abstract
The structures, infrared active OH stretching modes, and relative energies of OH-defects in ringwoodite (γ-Mg2SiO4) have been studied by first-principles calculations based on density functional theory (DFT). Two types of fully protonated cationic defects in normal spinel were considered at 0 and 20 GPa, i.e., [VMg(OH)2]x, [VSiOH)4]x defects. In addition, two defects associated with the partial inversion of the spinel structure have been investigated. The first one corresponds to two protons compensating a Mg substituted for Si in tetrahedral site, [MgSi(OH)2]x, whereas the second defect corresponds to a Mg vacancy located nearby a Mg-Si substitution, [VMg(OH)2MgSiSiMg]x. The infrared spectrum and evolution with pressure of these OH-defects make it possible to interpret the major IR absorption bands experimentally observed. The main absorption band at ~3150 cm-1 corresponds to protons located between the O-O pairs shared by 16c and 16d octahedra, instead of OH along the tetrahedral edges as usually proposed in the literature. The large width of this band is most likely related to the association of OH defects with the various cationic configurations related to the partial inversion of a vacancy-bearing spinel structure. The less intense band at ~3675 cm-1 is assigned to hydrogarnet-type defects with a protonation of the tetrahedral edges. This interpretation is consistent with an Mg/Si ratio lower than 2 and its weak variation as a function of water concentration, as experimentally observed. These results emphasize the importance of taking into account the structural relaxation experienced by defects, instead of using empirical correlation, to assign OH stretching bands to specific O-O pairs of the structure.
© 2015 by Walter de Gruyter Berlin/Boston
Artikel in diesem Heft
- Amorphous materials: Properties, structure, and durability. The viscosity of hydrous NaAlSi3O8 and granitic melts: Configurational entropy models
- Alteration mineralogy and the effect of acid-leaching on the Pb-isotope systematics of ocean-island basalts
- Color origin and heat evidence of paleontological bones: Case study of blue and gray bones from San Josecito Cave, Mexico
- Coexistence of pyroxenes jadeite, omphacite, and diopside/hedenbergite in an albite-omphacite rock from a serpentinite mélange in the Kurosegawa Zone of Central Kyushu, Japan
- Amphibole equilibria in mantle rocks: Determining values of mantle aH2O and implications for mantle H2O contents
- Experimental fluoridation of nanocrystalline apatite
- Dehydration dynamics of barrerite: An in situ synchrotron XRPD study
- Structural features in Tutton’s salts K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn
- Incorporation of water in iron-free ringwoodite: A first-principles study
- Temperature dependence of reflectance spectra and color values of hematite by in situ, high-temperature visible micro-spectroscopy
- Lattice thermal expansion of zircon-type LuPO4 and LuVO4: A comparative study
- Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 °C and pressure from 50 to 500 MPa
- Multi-analytical approach to solve the puzzle of an allanite-subgroup mineral from Kesebol, Västra Götaland, Sweden
- Dislocation modeling in calcium silicate perovskite based on the Peierls-Nabarro model
- Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites
- Adding further complexity to the polybasite structure: The role of Ag in the B layer of the -M2a2b2c polytype
- Structural position of H2O molecules and hydrogen bonding in anomalous 11 Å tobermorite
- Electronic structures of siderite (FeCO3) and rhodochrosite (MnCO3): Oxygen K-edge spectroscopy and hybrid density functional theory
- Crystal growth and the fast reaction paradox: Mathematical resolution and implications for habit and compositional zoning
- The composition of KLB-1 peridotite
- Crystal chemistry of the magnetite-ulvöspinel series
- New insights into the crystal structure and crystal chemistry of the zeolite phillipsite
- Letter: Octahedral cation distribution in palygorskite
Artikel in diesem Heft
- Amorphous materials: Properties, structure, and durability. The viscosity of hydrous NaAlSi3O8 and granitic melts: Configurational entropy models
- Alteration mineralogy and the effect of acid-leaching on the Pb-isotope systematics of ocean-island basalts
- Color origin and heat evidence of paleontological bones: Case study of blue and gray bones from San Josecito Cave, Mexico
- Coexistence of pyroxenes jadeite, omphacite, and diopside/hedenbergite in an albite-omphacite rock from a serpentinite mélange in the Kurosegawa Zone of Central Kyushu, Japan
- Amphibole equilibria in mantle rocks: Determining values of mantle aH2O and implications for mantle H2O contents
- Experimental fluoridation of nanocrystalline apatite
- Dehydration dynamics of barrerite: An in situ synchrotron XRPD study
- Structural features in Tutton’s salts K2[M2+(H2O)6](SO4)2, with M2+ = Mg, Fe, Co, Ni, Cu, and Zn
- Incorporation of water in iron-free ringwoodite: A first-principles study
- Temperature dependence of reflectance spectra and color values of hematite by in situ, high-temperature visible micro-spectroscopy
- Lattice thermal expansion of zircon-type LuPO4 and LuVO4: A comparative study
- Solubility of H2O and CO2 in ultrapotassic melts at 1200 and 1250 °C and pressure from 50 to 500 MPa
- Multi-analytical approach to solve the puzzle of an allanite-subgroup mineral from Kesebol, Västra Götaland, Sweden
- Dislocation modeling in calcium silicate perovskite based on the Peierls-Nabarro model
- Molecular dynamics insight into the cointercalation of hexadecyltrimethyl-ammonium and acetate ions into smectites
- Adding further complexity to the polybasite structure: The role of Ag in the B layer of the -M2a2b2c polytype
- Structural position of H2O molecules and hydrogen bonding in anomalous 11 Å tobermorite
- Electronic structures of siderite (FeCO3) and rhodochrosite (MnCO3): Oxygen K-edge spectroscopy and hybrid density functional theory
- Crystal growth and the fast reaction paradox: Mathematical resolution and implications for habit and compositional zoning
- The composition of KLB-1 peridotite
- Crystal chemistry of the magnetite-ulvöspinel series
- New insights into the crystal structure and crystal chemistry of the zeolite phillipsite
- Letter: Octahedral cation distribution in palygorskite
