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Title: Ab initio thermodynamics of magnesium carbonates and hydrates in water-saturated supercritical CO 2 and CO 2 -rich regions

Authors:
; ;
Publication Date:
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1358936
Resource Type:
Journal Article: Publisher's Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 434; Journal Issue: C; Related Information: CHORUS Timestamp: 2017-10-03 21:36:03; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
Netherlands
Language:
English

Citation Formats

Chaka, Anne M., Felmy, Andrew R., and Qafoku, Odeta. Ab initio thermodynamics of magnesium carbonates and hydrates in water-saturated supercritical CO 2 and CO 2 -rich regions. Netherlands: N. p., 2016. Web. doi:10.1016/j.chemgeo.2016.04.005.
Chaka, Anne M., Felmy, Andrew R., & Qafoku, Odeta. Ab initio thermodynamics of magnesium carbonates and hydrates in water-saturated supercritical CO 2 and CO 2 -rich regions. Netherlands. doi:10.1016/j.chemgeo.2016.04.005.
Chaka, Anne M., Felmy, Andrew R., and Qafoku, Odeta. Thu . "Ab initio thermodynamics of magnesium carbonates and hydrates in water-saturated supercritical CO 2 and CO 2 -rich regions". Netherlands. doi:10.1016/j.chemgeo.2016.04.005.
@article{osti_1358936,
title = {Ab initio thermodynamics of magnesium carbonates and hydrates in water-saturated supercritical CO 2 and CO 2 -rich regions},
author = {Chaka, Anne M. and Felmy, Andrew R. and Qafoku, Odeta},
abstractNote = {},
doi = {10.1016/j.chemgeo.2016.04.005},
journal = {Chemical Geology},
number = C,
volume = 434,
place = {Netherlands},
year = {Thu Sep 01 00:00:00 EDT 2016},
month = {Thu Sep 01 00:00:00 EDT 2016}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1016/j.chemgeo.2016.04.005

Citation Metrics:
Cited by: 2works
Citation information provided by
Web of Science

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  • An ab initio thermodynamic framework for predicting properties of hydrated magnesium carbonate minerals has been developed using density-functional theory linked to macroscopic thermodynamics through the experimental chemical potentials for MgO, water, and CO2. Including semiempirical dispersion via the Grimme method and small corrections to the generalized gradient approximation of Perdew, Burke, and Ernzerhof for the heat of formation yields a model with quantitative agreement for the benchmark minerals brucite, magnesite, nesquehonite, and hydromagnesite. The model shows how small differences in experimental conditions determine whether nesquehonite, hydromagnesite, or magnesite is the result of laboratory synthesis from carbonation of brucite, and whatmore » transformations are expected to occur on geological time scales. Because of the reliance on parameter-free first principles methods, the model is reliably extensible to experimental conditions not readily accessible to experiment and to any mineral composition for which the structure is known or can be hypothesized, including structures containing defects, substitutions, or transitional structures during solid state transformations induced by temperature changes or processes such as water, CO2, or O2 diffusion. Demonstrated applications of the ab initio thermodynamic framework include an independent means to evaluate differences in thermodynamic data for lansfordite, predicting the properties of Mg analogs of Ca-based hydrated carbonates monohydrocalcite and ikaite which have not been observed in nature, and an estimation of the thermodynamics of barringtonite from the stoichiometry and a single experimental observation.« less
  • A detailed ab initio computational study of H[sub 2] addition to Vaska-type complexes (trans-Ir(PR[sub 3])[sub 2](CO)X) has been conducted. The calculated relative energies of addition agree very well with known experimental values. The computed prediction for X = CN has been verified. The authors conclude that the thermodynamics of H[sub 2] addition is dominated primarily by [pi]-interactions and, in contrast to commonly held views of this reaction, increased [pi]-donation decreases the exothermicity of H[sub 2] addition. 19 refs., 1 tab.
  • Ab initio electronic structure calculations are used to study substituent effects in Vaska-type complexes, trans-IrL{sub 2}(CO)X (1-X) (X = F, Cl, Br, I, CN, H, CH{sub 3}, SiH{sub 3}, OH, and SH; L = PH{sub 3}). Both the electron affinity and the ionization potential of 1-X are computed to increase upon descending the halogen series of complexes, which indicates, surprisingly, that the complexes with more electronegative halogens are more difficult to reduce and easier to oxidize. The computed electron affinity trend is consistent with the half-wave reduction potential trend known for 1-X (L = PPh{sub 3}; X = F, Cl,more » Br, and I). Computed carbonyl stretch frequencies for 1-X are greater than experimental values (L = PPh{sub 3}), but observed trends are well reproduced. The redox and spectroscopic trends are discussed in terms of the substituent effects on the electronic structure of 1-X, particularly as revealed in the molecular orbital energy level diagrams of these complexes. The reaction energy for H{sub 2} addition to 1-X, leading to the cis,trans-(H){sub 2}IrL{sub 2}(CO)X (2-X) product, has been computed. After electron correlation effects are included (MP4(SDTQ)), the reaction enthalpy computed for 1-CI is {minus}18.4 kcal/mol (L = PH{sub 3}) as compared to a reported experimental value of {minus}14 kcal/mol (L = PPh{sub 3}). Compared with available experimental data, the electronic effects of L(L = PH{sub 3}, NH{sub 3}, or AsH{sub 3}) and X on the thermodynamics of the H{sub 2} addition reaction are accurately reproduced by the model calculations at all levels of theory (HF and MPn). Formation of the hypothetical products cis,trans- and trans,trans-(H){sub 2}IrL{sub 2}(CO)X(2-X and 3-X) (X = BH{sub 2}, NH{sub 2}, and PH{sub 2}) is used to demonstrate that {pi}-acceptor substituents promote the H{sub 2} addition reaction to 1-X while {pi}-donor substituents disfavor addition.« less
  • New, full-dimensional potential energy surfaces (PESs), obtained using precise least-squares fitting of high-level electronic energy databases, are reported for intrinsic H{sub 2}(H{sub 2}O) two-body and H{sub 2}(H{sub 2}O){sub 2} three-body potentials. The database for H{sub 2}(H{sub 2}O) consists of approximately 44 000 energies at the coupled cluster singles and doubles plus perturbative triples (CCSD(T))-F12a/haQZ (aug-cc-pVQZ for O and cc-pVQZ for H) level of theory, while the database for the three-body interaction consists of more than 36 000 energies at the CCSD(T)-F12a/haTZ (aug-cc-pVTZ for O, cc-pVTZ for H) level of theory. Two precise potentials are based on the invariant-polynomial technique and are comparedmore » to computationally faster ones obtained via “purified” symmetrization. All fits use reduced permutational symmetry appropriate for these non-covalent interactions. These intrinsic potentials are employed together with existing ones for H{sub 2}, H{sub 2}O, and (H{sub 2}O){sub 2}, to obtain full PESs for H{sub 2}(H{sub 2}O) and H{sub 2}(H{sub 2}O){sub 2}. Properties of these full PESs are presented, including a diffusion Monte Carlo calculation of the zero-point energy and wavefunction, and dissociation energy of the H{sub 2}(H{sub 2}O) dimer. These PESs together with an existing one for water clusters are used in a many-body representation of the PES of hydrogen clathrate hydrates, illustrated for H{sub 2}@(H{sub 2}O){sub 20}. An analysis of this hydrate is presented, including the electronic dissociation energy to remove H{sub 2} from the calculated equilibrium structure.« less