First-principles modeling of chlorine isotope fractionation between chloride-bearing molecules and minerals

Balan, Etienne; Créon, Laura; Sanloup, C.; Adnot, Jérôme; Blanchard, Marc; Paulatto, Lorenzo; Bureau, Hélène

doi:10.1016/j.chemgeo.2019.07.032

Cited by 22 publications

(11 citation statements)

References 79 publications

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“…It is expected that the theoretical stretching frequencies obtained in the present study overestimate the frequencies experimentally observed at ambient temperature by typically 10 to 50 cm −1 , as observed in quartz (Jollands et al, 2020). A stronger overestimation, amounting to 125 cm −1 , has, however, been recently observed for OH defects in corundum (Balan, 2020). We will see in the following that the theoretical frequencies of OH defects in diopside are systematically upshifted by ∼ 50 cm −1 compared to their experimental counterparts (Fig.…”

Section: General Properties Of Oh-bearing Defects In Diopsidecontrasting

confidence: 49%

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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Section: General Properties Of Oh-bearing Defects In Diopsidecontrasting

confidence: 49%

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

et al. 2020

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“…The substitution of boron or aluminum for silicon has been experimentally investigated and revealed a number of associated OH-stretching bands. Quartz samples grown in high-B systems display a characteristic band at 3596 cm −1 that has been ascribed to a (B,OH) defect (Staats and Kopp, 1974;Thomas et al, 2009;Baron et al, 2015). This band has a dominant polarization in the (001) plane and a weaker contribution parallel to the [001] direction (Thomas et al, 2009;Baron et al, 2015).…”

Section: Oh Defects Associated With Chemical Impuritiesmentioning

confidence: 99%

“…Quartz samples grown in high-B systems display a characteristic band at 3596 cm −1 that has been ascribed to a (B,OH) defect (Staats and Kopp, 1974;Thomas et al, 2009;Baron et al, 2015). This band has a dominant polarization in the (001) plane and a weaker contribution parallel to the [001] direction (Thomas et al, 2009;Baron et al, 2015). In the quartzalbite-water or granite-water systems, IR spectra of quartz display three bands polarized in the (001) plane and observed at 3313, 3379 and 3431 cm −1 (Stalder and Konzett, 2012).…”

Section: Oh Defects Associated With Chemical Impuritiesmentioning

confidence: 99%

“…In this study, only Li + cations have been considered, i.e., forming defects with the stoichiometry LiOH. Experimentally, the infrared spectrum of quartz samples grown in Li-bearing systems displays a characteristic band at 3483 cm −1 (Baron et al, 2015;Frigo et al, 2016).…”

Section: Oh Defects Associated With Chemical Impuritiesmentioning

confidence: 99%

“…The bands at 3431, 3379 and 3313 cm −1 are assigned to OH groups related to the substitution of Al 3+ for Si 4+ , based on a correlation between Al and H (Kats, 1962), studies of paramagnetic defects by electron spin resonance following irradiation (Sibley et al, 1979;Halliburton et al, 1981) and their presence following synthesis in the quartz-albite system (Stalder and Konzett, 2012). Quartz synthesized in systems with elevated boron shows a band at 3596 cm −1 , thus assigned to OH associated with the B 3+ -for-Si 4+ substitution (Staats and Kopp, 1974;Thomas et al, 2009;Baron et al, 2015). Finally, quartz samples produced in systems with high Li display a band at 3483 cm −1 , which is therefore associated with Li + ions located in the structural channels of quartz (Kats, 1962;Frigo et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

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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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Experimental study of chemical evolution and isotope fractionation of Cl and Br in pore water expelled during strong clay compaction

Strydom

Sterpenich

Grgic

et al. 2022

Applied Geochemistry

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First-principles modeling of chlorine isotope fractionation between chloride-bearing molecules and minerals

Cited by 22 publications

References 79 publications

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

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

Structure and theoretical infrared spectra of OH defects in quartz

Experimental study of chemical evolution and isotope fractionation of Cl and Br in pore water expelled during strong clay compaction

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