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Title: Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective

Abstract

The edges of montmorillonite (MMT) react strongly with metals and organic matter, but the atomic structure of the edge and its surface complexes are not unambiguous since the experimental isolation of the edge is challenging. In this study, we introduce an atomistic model of a Na MMT edge that is suitable for classical molecular dynamics (MD) simulations, in particular for the B edge, a representative edge surface of 2:1 phyllosilicates. Our model possesses the surface groups identified through density functional theory (DFT) geometry optimizations performed with variation in the structural charge deficit and Mg substitution sites. The edge structure of the classical MD simulations agreed well with previous DFT-based MD simulation results. Our MD simulations revealed an extensive H-bond network stabilizing the Na-MMT edge surface, which required an extensive simulation trajectory. Some Na counter ions formed inner-sphere complexes at two edge sites. The stronger edge site coincided with the exposed vacancy in the dioctahedral sheet; a weaker site was associated with the cleaved hexagonal cavity of the tetrahedral sheet. The six-coordinate Na complexes were not directly associated with the Mg edge site. Our simulations have demonstrated the heterogeneous surface structures, the distribution of edge surface groups, and the reactivity ofmore » the MMT edge.« less

Authors:
 [1]; ORCiD logo [1];  [1]
  1. Kangwon National Univ., Chuncheon (Korea). Dept. of Geology; Kangwon National Univ., Chuncheon (Korea). Critical Zone Frontier Research Lab. (CFRL)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1524085
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Minerals
Additional Journal Information:
Journal Volume: 7; Journal Issue: 5; Journal ID: ISSN 2075-163X
Publisher:
MDPI
Country of Publication:
United States
Language:
English
Subject:
clay edge; mineral surface; Na-montmorillonite; nanoporous minerals; molecular dynamics; density functional theory; computational geochemistry

Citation Formats

Newton, Aric G., Lee, Jin -Yong, and Kwon, Kideok D. Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective. United States: N. p., 2017. Web. doi:10.3390/min7050078.
Newton, Aric G., Lee, Jin -Yong, & Kwon, Kideok D. Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective. United States. doi:10.3390/min7050078.
Newton, Aric G., Lee, Jin -Yong, and Kwon, Kideok D. Fri . "Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective". United States. doi:10.3390/min7050078. https://www.osti.gov/servlets/purl/1524085.
@article{osti_1524085,
title = {Na-Montmorillonite Edge Structure and Surface Complexes: An Atomistic Perspective},
author = {Newton, Aric G. and Lee, Jin -Yong and Kwon, Kideok D.},
abstractNote = {The edges of montmorillonite (MMT) react strongly with metals and organic matter, but the atomic structure of the edge and its surface complexes are not unambiguous since the experimental isolation of the edge is challenging. In this study, we introduce an atomistic model of a Na MMT edge that is suitable for classical molecular dynamics (MD) simulations, in particular for the B edge, a representative edge surface of 2:1 phyllosilicates. Our model possesses the surface groups identified through density functional theory (DFT) geometry optimizations performed with variation in the structural charge deficit and Mg substitution sites. The edge structure of the classical MD simulations agreed well with previous DFT-based MD simulation results. Our MD simulations revealed an extensive H-bond network stabilizing the Na-MMT edge surface, which required an extensive simulation trajectory. Some Na counter ions formed inner-sphere complexes at two edge sites. The stronger edge site coincided with the exposed vacancy in the dioctahedral sheet; a weaker site was associated with the cleaved hexagonal cavity of the tetrahedral sheet. The six-coordinate Na complexes were not directly associated with the Mg edge site. Our simulations have demonstrated the heterogeneous surface structures, the distribution of edge surface groups, and the reactivity of the MMT edge.},
doi = {10.3390/min7050078},
journal = {Minerals},
number = 5,
volume = 7,
place = {United States},
year = {2017},
month = {5}
}

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Works referenced in this record:

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