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Title: Molecular dynamics simulations of the orthoclase (001)- and (010)-water interfaces

Abstract

Molecular dynamics simulations of water in contact with the (001) and (010) surfaces of orthoclase (KAlSi3O8) were carried out to investigate the structure and dynamics of the feldspar-water interface, contrast the intrinsic structural properties of the two surfaces, and provide a basis for future work on the diffusion of ions and molecules in microscopic mineral fractures. Electron density profiles were computed from the molecular dynamics trajectories and compared with those derived experimentally from high-resolution X-ray reflectivity measurements by Fenter and co-workers (Fenter et al., 2003a). For each surface, three scenarios were considered whereby the interfacial species is potassium, water, or a hydronium ion. Excellent agreement was obtained for the (001) surface when potassium is the predominant interfacial species. Good agreement was found for the (010) surface with some discrepancies which could be due in part to the fact that our model does not take into account the increased roughness of the (010) surface compared to the (001) surface. The two surfaces showed similarities in the extent of water ordering at the interface, the activation energies for water and potassium desorption, and the adsorption localization of interfacial species. However, there are also important differences between the two surfaces in the coordinationmore » of a given adsorbed species, adsorption sites density, and the propensity for water molecules in the adsorbed and first hydration layers to coordinate to surface bridging oxygen atoms. These differences may have implications for the extent of dissolution in the proton-promoted regime since hydrolysis of Si(Al)-O-Si(Al) bonds is thought to be the major dissolution mechanism.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
927967
Report Number(s):
PNNL-SA-57227
Journal ID: ISSN 0016-7037; GCACAK; KP1504010; TRN: US0804677
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta, 72(6):1481-1497
Additional Journal Information:
Journal Volume: 72; Journal Issue: 6; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ADSORPTION; ATOMS; DESORPTION; DIFFUSION; DISSOLUTION; ELECTRON DENSITY; FRACTURES; HYDRATION; HYDROLYSIS; ORTHOCLASE; OXONIUM IONS; OXYGEN; POTASSIUM; REFLECTIVITY; ROUGHNESS; TRAJECTORIES; WATER; molecular dynamics; orthoclase surfaces; feldspar; potassium, adsorption, electron density profile

Citation Formats

Kerisit, Sebastien N, Liu, Chongxuan, and Ilton, Eugene S. Molecular dynamics simulations of the orthoclase (001)- and (010)-water interfaces. United States: N. p., 2008. Web. doi:10.1016/j.gca.2007.12.014.
Kerisit, Sebastien N, Liu, Chongxuan, & Ilton, Eugene S. Molecular dynamics simulations of the orthoclase (001)- and (010)-water interfaces. United States. doi:10.1016/j.gca.2007.12.014.
Kerisit, Sebastien N, Liu, Chongxuan, and Ilton, Eugene S. Sat . "Molecular dynamics simulations of the orthoclase (001)- and (010)-water interfaces". United States. doi:10.1016/j.gca.2007.12.014.
@article{osti_927967,
title = {Molecular dynamics simulations of the orthoclase (001)- and (010)-water interfaces},
author = {Kerisit, Sebastien N and Liu, Chongxuan and Ilton, Eugene S},
abstractNote = {Molecular dynamics simulations of water in contact with the (001) and (010) surfaces of orthoclase (KAlSi3O8) were carried out to investigate the structure and dynamics of the feldspar-water interface, contrast the intrinsic structural properties of the two surfaces, and provide a basis for future work on the diffusion of ions and molecules in microscopic mineral fractures. Electron density profiles were computed from the molecular dynamics trajectories and compared with those derived experimentally from high-resolution X-ray reflectivity measurements by Fenter and co-workers (Fenter et al., 2003a). For each surface, three scenarios were considered whereby the interfacial species is potassium, water, or a hydronium ion. Excellent agreement was obtained for the (001) surface when potassium is the predominant interfacial species. Good agreement was found for the (010) surface with some discrepancies which could be due in part to the fact that our model does not take into account the increased roughness of the (010) surface compared to the (001) surface. The two surfaces showed similarities in the extent of water ordering at the interface, the activation energies for water and potassium desorption, and the adsorption localization of interfacial species. However, there are also important differences between the two surfaces in the coordination of a given adsorbed species, adsorption sites density, and the propensity for water molecules in the adsorbed and first hydration layers to coordinate to surface bridging oxygen atoms. These differences may have implications for the extent of dissolution in the proton-promoted regime since hydrolysis of Si(Al)-O-Si(Al) bonds is thought to be the major dissolution mechanism.},
doi = {10.1016/j.gca.2007.12.014},
journal = {Geochimica et Cosmochimica Acta, 72(6):1481-1497},
issn = {0016-7037},
number = 6,
volume = 72,
place = {United States},
year = {2008},
month = {3}
}