Theoretical Raman spectrum and anharmonicity of tetrahedral OH defects in hydrous forsterite

Balan, Etienne; Blanchard, Marc; Lazzeri, Michele; Ingrin, Jannick

doi:10.1127/ejm/2017/0029-2599

Cited by 15 publications

(6 citation statements)

References 71 publications

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“…6) the positions of the OH bands at 3612 cm −1 (very weak), 3580, 3566, and 3545 cm −1 (strong) and at 3479 + 3459 cm −1 (weak) do not vary significantly, and their intensities increase proportionally to the measured water content. Note that these bands are very close to those already observed by Bolfan-Casanova et al (2014) with Raman spectroscopy for hydrothermally annealed forsterite and theoretically expected by Balan et al (2017). Even if it is OH that is observed, in the following we will refer to it as water.…”

Section: Raman Spectrasupporting

confidence: 85%

Effect of oxygen fugacity on the storage of water in wadsleyite and olivine in H and H–C fluids and implications for melting atop the transition zone

Bolfan-Casanova,

Martinek,

Manthilake

et al. 2023

Eur. J. Mineral.

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Abstract. This study aims to experimentally constrain the water storage capacities of olivine and wadsleyite at a depth near 410 km (12–14 GPa) under water-saturated conditions, as a function of temperature, oxygen fugacity, and the presence of carbon (molar H / C of 2). Experiments have been conducted in the multi-anvil press, with sealed double capsules to preserve fluids, at 1200 to 1400 ∘C and three different oxygen fugacities fixed at the rhenium–rhenium oxide buffer (RRO), nickel–nickel oxide buffer (NNO), and iron-wüstite (IW) for oxidizing, intermediate, and reducing conditions, respectively. The water contents of minerals were measured by Raman spectroscopy that allows a very small beam size to be used and were cross-checked on a few samples with NanoSIMS analyses. We observe an effect, although slight, of fO2 on the water storage capacity of both wadsleyite and olivine and also on their solidus temperatures. At 1200 ∘C, the storage capacity of the nominally anhydrous minerals (NAMS) increases with increasing oxygen fugacity (from the IW to the RRO buffer) from 1 wt % to 1.5 wt % H2O in wadsleyite and from 0.1 wt % to 0.2 wt % in olivine, owing to the increase in H2O / H2 speciation in the fluid, whereas at 1400 ∘C the storage capacity decreases from 1 wt % to 0.75 wt % H2O in wadsleyite and down to 0.03 wt % for olivine. At high temperature, the water storage capacity is lowered due to melting, and the more oxidized the conditions are the more the solidus is depressed. Still, at 1400 ∘C and IW, wadsleyite can store substantial amounts of water: 0.8 wt % to 1 wt % H2O. The effect of carbon is to decrease water storage capacity in both wadsleyite and olivine by an average factor 2 at 1300–1400 ∘C. The trends in water storage as a function of fO2 and C presence are confirmed by NanoSIMS measurements. The solidus at IW without C is located between 1300 and 1400 ∘C in the wadsleyite stability field and drops to temperatures below 1300 ∘C in the olivine stability field. With the addition of C, the solidus is found between 1200 and 1300 ∘C in both olivine and wadsleyite stability fields.

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Section: Raman Spectrasupporting

confidence: 85%

Effect of oxygen fugacity on the storage of water in wadsleyite and olivine in H and H–C fluids and implications for melting atop the transition zone

Bolfan-Casanova,

Martinek,

Manthilake

et al. 2023

Eur. J. Mineral.

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“…The ionic cores were described using optimized norm-conserving Vanderbilt (ONCV) pseudopotentials (Hamann, 2013;Schlipf and Gygi, 2015). Cutoffs of 80 and 480 Ry on the electronic wave functions and charge density, respectively, were used as in Balan et al (2019). Structural properties of α-quartz (SG P3 2 21) were determined using its primitive cell (9 atoms), whereas 2 × 2 × 2 supercells (72 atoms) containing up to four hydrogen atoms were used to model the OH defects.…”

Section: Methodsmentioning

confidence: 99%

Structure and theoretical infrared spectra of OH defects in quartz

2020

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Abstract. The infrared spectra of natural quartz, and synthetic quartz produced in conditions relevant to natural environments, generally contain some association of OH-stretching absorption bands at 3596, 3585, 3483, 3431, 3379 and 3313 cm−1, and/or a broad band at ∼ 3400 cm−1. In this study, a series of OH-bearing defects has been theoretically investigated from first principles within the density functional theory framework. The optimized structure, infrared spectroscopic properties and relative energy of defect configurations have been determined. Comparison with experimental observations enables the identification of atomic-scale configurations related to the experimentally observed OH-stretching bands. Consistent with previous interpretations, the results confirm the assignment of the bands at 3596 and 3483 cm−1 to OH defects associated with B3+ substituting for Si4+ and to OH defects associated with Li+ cations located in the structural channels, respectively. They also confirm the assignment of the bands at 3313 and 3379 cm−1 to OH associated with the Al3+-for-Si4+ substitution and, by implication, the previously given interpretation of the 3431 cm−1 band in terms of Fermi resonance. The band at 3585 cm−1 does not appear to be related to a hydrogarnet-type defect, as has been proposed previously, but potentially corresponds to isolated OH− groups bridging two Si atoms, where the charge compensation is ensured by a nonlocal mechanism.

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“…The modeling scheme used the generalized gradient approximation (GGA) to the exchangecorrelation functional as proposed by Perdew, Burke and Ernzerhof (PBE functional;Perdew et al, 1996), and periodic boundary conditions. The ionic cores were described using optimized norm-conserving Vanderbilt (ONCV) pseudopotentials (Hamann, 2013; Schlipf and Gygi, 2015) with a 80 Ry cutoff on the electronic wave functions, as in Balan et al (2019) and Jollands et al (2020). Structural properties of OH-bearing defects were determined using 1×1×2 diopside supercells (80 atoms) containing up to four hydrogen atoms.…”

Section: Theoretical Modeling Of Oh Defectsmentioning

confidence: 99%

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

et al. 2020

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Abstract. Hydrous defects in diopside (CaMgSi2O6) play an important role in the water budget of the Earth's mantle. Related OH-stretching modes lead to a variety of infrared absorption bands observed in natural or experimental samples. In the present study, we report new low-temperature infrared spectra of reference natural diopside samples in the OH-stretching range. In parallel, the structure and vibrational properties of a series of OH-bearing defects in diopside are theoretically determined at the density functional theory level. The infrared spectra make it possible to resolve additional bands in the region above 3600 cm−1 and reveal that their anharmonic behavior differs from that of the bands at lower frequency. A comparison of theoretical results with experimental data makes it possible to propose atomic-scale geometries corresponding to observed OH-stretching bands. It confirms that the bands observed at 3620–3651 cm−1 are related to M3+ ions substituted for Si in tetrahedral sites, while the 3420 cm−1 band is associated with the Na+ for Ca2+ substitution. In both cases, H+ incorporation compensates the charge deficit due to the heterovalent substitution. The other major mechanism of water incorporation in diopside relates to the charge compensation of cationic vacancies, among which Ca vacancies play a central role. The 3357 cm−1 band corresponds to doubly protonated Ca vacancies in pure diopside. In experimental diopside-bearing trivalent cations, the bands at 3432–3460 cm−1 correspond to singly protonated Ca vacancies with a nearby octahedral M3+ ion, while the 3310 cm−1 band likely involves a more remote charge compensation by M3+ ions. More complex defects associating Ca vacancies with tetrahedral M3+ and octahedral Ti4+ ions are proposed for the bands observed between 3500 and 3600 cm−1 in natural diopside. The Fe2+ for Mg2+ and Fe2+ for Ca2+ substitutions are also found to affect nearby OH-bearing defects, causing a shift and broadening of OH stretching bands in chemically more complex diopside samples.

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Theoretical Raman spectrum and anharmonicity of tetrahedral OH defects in hydrous forsterite

Cited by 15 publications

References 71 publications

Effect of oxygen fugacity on the storage of water in wadsleyite and olivine in H and H–C fluids and implications for melting atop the transition zone

Effect of oxygen fugacity on the storage of water in wadsleyite and olivine in H and H–C fluids and implications for melting atop the transition zone

Structure and theoretical infrared spectra of OH defects in quartz

Low-temperature infrared spectrum and atomic-scale structure of hydrous defects in diopside

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