CaltechAUTHORS
  A Caltech Library Service

Structural roles of CO_2 and [CO_3]^(2-) in fully polymerized sodium aluminosilicate melts and glasses

Kubicki, J. D. and Stolper, E. M. (1995) Structural roles of CO_2 and [CO_3]^(2-) in fully polymerized sodium aluminosilicate melts and glasses. Geochimica et Cosmochimica Acta, 59 (4). pp. 683-698. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20120821-081626673

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20120821-081626673

Abstract

Ab initio, molecular orbital calculations of the structures, energetics, and vibrational spectra of six T_2O_(br)-CO_2 clusters and five T-[CO_3]-T clusters (T = Al or Si, with and without Na^+ present) have been completed using a 3–21G^(∗∗) basis set and the Gaussian 92 program to evaluate possible configurations of CO_2 molecules and carbonate groups in melts and glasses on the NaAlO_2-SiO_2 join. Based on these calculations, we developed the following hypothesis for the solution mechanisms of CO_2 molecules and carbonate groups in fully polymerized melts and glasses on this join. Molecular CO2 is weakly bound to bridging oxygen atoms in T_2O_(br)-CO_2 clusters. Calculated energetics indicate that molecular CO_2 is more strongly bonded when associated with smaller angle T-O-T linkages, and thus may preferentially bond to linkages where at least one T = Al^(3+). [CO_3]^(2−) is most likely present in T-[CO_3]-T linkages. Si-[CO_3]-Al linkages probably form in melts toward the silica-rich end of the NaAlO_2-SiO_2 join; Si-[NaCO_3]-Al and/or Al-[CO_3]-Al become more significant with increasing NaAlO_2 content. The experimentally observed increase in [CO_3]^(2-)/CO_2 ratio accompanying higher NaAlO_2 compositions can be understood in terms of the predicted increasingly negative ΔG° for T_2O_(br)-CO_2 → T-[CO_3]-T reactions when Si-[NaCO_3]-Al and Al-[CO_3]-Al rather than Si-[CO_3]-Si and Si-[CO_3]-Al are the reaction products. In addition, a reaction pathway with a low activation energy was calculated for forming T-[CO_3]-T linkages from T_2O_(br)-CO_2 linkages. This model is consistent with available information on the vibrational and NMR spectra of C-bearing Na-aluminosilicate glasses, and on the relative proportions in these glasses of carbonate and molecular CO_2 and their dependence on pressure, temperature, and composition.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/0016-7037(94)00317-FDOIUNSPECIFIED
http://www.sciencedirect.com/science/article/pii/001670379400317FPublisherUNSPECIFIED
Additional Information:© 1995 Elsevier Science Ltd. Received 22 March 1994. Accepted 14 September 1994. Available online 19 April 2002. Editorial handling: P. C. Hess. The authors acknowledge the support of NASA grant number NAGW 2320 and NSF grant EAR91-54186 (E. M. Stolper). J.D. Kubicki also acknowledges NSF grant EAR91-17946 (G. A. Blake). Computational facilities were provided by the Molecular Simulation Center (W. A. Goddard) of the Beckman Institute at Caltech and the Jet Propulsion Laboratory. Insightful reviews by A. B. Belonoshko and S.C. Kohn are also greatly appreciated.
Funders:
Funding AgencyGrant Number
NASANAGW 2320
NSFEAR91-54186
NSFEAR91-17946
Record Number:CaltechAUTHORS:20120821-081626673
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120821-081626673
Official Citation:J.D. Kubicki, E.M. Stolper, Structural roles of CO2 and [CO3]2− in fully polymerized sodium aluminosilicate melts and glasses, Geochimica et Cosmochimica Acta, Volume 59, Issue 4, February 1995, Pages 683-698, ISSN 0016-7037, 10.1016/0016-7037(94)00317-F. (http://www.sciencedirect.com/science/article/pii/001670379400317F)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:33388
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:21 Aug 2012 15:49
Last Modified:21 Aug 2012 15:49

Repository Staff Only: item control page