First-principles modeling of sulfate incorporation and 34S/32S isotopic fractionation in different calcium carbonates

Temperature relations of b-factors for 18O/16O substitutions in TiO2 polymorphs have been determined using the density functional theory (DFT): 1000lnbrt(18O/16O) = 6,93039x - 0,08158x2 + 0,00116x3 + 0,08305*P, 1000lnbant(18O/16O) = 7,34275x - 0,09906x2 + 0,00153x3 + 0,08027*P, 1000lnbbrk(18O/16O) = 7,19088x - 009157x2 + 0,00139x3 + 0,07601*P, x = 106/T(K)2, P - pressure (GPa). The relations can be applied for isotope thermometry if combined with -factors of coexisting phases.

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Equilibrium isotopic fractionation in the kaolinite, quartz, water system: Prediction from first-principles density-functional theory

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2007.04.012 ◽

2007 ◽

Vol 71 (13) ◽

pp. 3170-3181 ◽

Cited By ~ 111

Author(s):

Merlin Méheut ◽

Michele Lazzeri ◽

Etienne Balan ◽

Francesco Mauri

Keyword(s):

Density Functional Theory ◽

First Principles ◽

Density Functional ◽

Isotopic Fractionation ◽

Water System ◽

Functional Theory

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First-principles calculation of H/D isotopic fractionation between hydrous minerals and water

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2010.04.020 ◽

2010 ◽

Vol 74 (14) ◽

pp. 3874-3882 ◽

Cited By ~ 32

Author(s):

Merlin Méheut ◽

Michele Lazzeri ◽

Etienne Balan ◽

Francesco Mauri

Keyword(s):

First Principles ◽

Isotopic Fractionation ◽

First Principles Calculation ◽

Hydrous Minerals

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OCS photolytic isotope effects from first principles: sulfur and carbon isotopes, temperature dependence and implications for the stratosphere

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-1511-2013 ◽

2013 ◽

Vol 13 (3) ◽

pp. 1511-1520 ◽

Cited By ~ 20

Author(s):

J. A. Schmidt ◽

M. S. Johnson ◽

S. Hattori ◽

N. Yoshida ◽

S. Nanbu ◽

...

Keyword(s):

Cross Sections ◽

First Principles ◽

Isotope Effects ◽

Isotopic Fractionation ◽

Data Sets ◽

Mechanical Formalism ◽

Model Study ◽

Quantum Mechanical Formalism ◽

Uv Excitation ◽

Good Agreement

Abstract. The isotopic fractionation in OCS photolysis is studied theoretically from first principles. UV absorption cross sections for OCS, OC33S, OC34S, OC36S and O13CS are calculated using the time-depedent quantum mechanical formalism and a recently developed ab-initio description of the photodissociation of OCS which takes into account the lowest four singlet and lowest four triplet electronic states. The calculated isotopic fractionations as a function of wavelength are in good agreement with recent measurements by Hattori et al. (2011) and indicate that photolysis leads to only a small enrichment of 34S in the remaining OCS. The photodissociation dynamics provide strong evidence that the photolysis quantum yield is unity at all wavelengths for atmospheric UV excitation, for all isotopologues. A simple stratospheric model is constructed taking into account the main sink reactions of OCS and it is found that overall stratospheric removal slightly favors light OCS in constrast to the findings of Leung et al. (2002). These results show, based on isotopic considerations, that OCS is an acceptable source of background stratosperic sulfate aerosol in agreement with a recent model study of of Brühl et al. (2012). The 13C isotopic fractionation due to photolysis of OCS in the upper stratosphere is significant and will leave a clear signal in the remaining OCS making it a candidate for tracing using the ACE-FTS and MIPAS data sets.

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First-principles investigation of equilibrium isotopic fractionation of O- and Si-isotopes between refractory solids and gases in the solar nebula

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2011.12.029 ◽

2012 ◽

Vol 319-320 ◽

pp. 118-127 ◽

Cited By ~ 24

Author(s):

Marc Javoy ◽

Etienne Balan ◽

Merlin Méheut ◽

Marc Blanchard ◽

Michele Lazzeri

Keyword(s):

First Principles ◽

Solar Nebula ◽

Isotopic Fractionation ◽

Si Isotopes

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Isotope effects in N<sub>2</sub>O photolysis from first principles

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-8965-2011 ◽

2011 ◽

Vol 11 (17) ◽

pp. 8965-8975 ◽

Cited By ~ 34

Author(s):

J. A. Schmidt ◽

M. S. Johnson ◽

R. Schinke

Keyword(s):

Experimental Data ◽

Potential Energy ◽

Cross Sections ◽

First Principles ◽

Potential Energy Surfaces ◽

Isotope Effects ◽

Isotopic Fractionation ◽

Energy Surfaces ◽

First Time ◽

Wavepacket Propagation

Abstract. For the first time, accurate first principles potential energy surfaces allow N2O cross sections and isotopic fractionation spectra to be derived that are in agreement with all available experimental data, extending our knowledge to a much broader range of conditions. Absorption spectra of rare N- and O-isotopologues (15N14N16O, 14N15N16O, 15N216O, 14N217O and 14N218O) calculated using wavepacket propagation are compared to the most abundant isotopologue (14N216O). The fractionation constants as a function of wavelength and temperature are in excellent agreement with experimental data. The study shows that excitations from the 3rd excited bending state, (0,3,0), and the first combination state, (1,1,0), are important for explaining the isotope effect at wavelengths longer than 210 nm. Only a small amount of the mass independent oxygen isotope anomaly observed in atmospheric N2O samples can be explained as arising from photolysis.

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