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Title: A structural coarse-grained model for clays using simple iterative Boltzmann inversion

Abstract

Cesium-137 is a crucial byproduct of nuclear energy generation and is environmentally threatening due to its long half-life and affinity for naturally occurring micaceous clays. Current experimental observations of illite and phlogopite mica indicate that Cs+ is capable of exchanging with K+ bound in the anhydrous interlayers of layered silicates, forming sharp exchange fronts, leading to interstratification of Cs- and K-illite. We introduce here a coarse-grained (CG) model of the anhydrous illite interlayer developed using iterative Boltzmann inversion that qualitatively and quantitatively reproduces features of a previously proposed feedback mechanism of ion exchange. The CG model represents a 70-fold speedup over all-atom models of clay systems and predicts interlayer expansion for K-illite near ion exchange fronts. Contrary to the longstanding theory that ion exchange in a neighboring layer increases the binding of K in lattice counterion sites leading to interstratification, we find that the presence of neighboring exchanged layers leads to short-range structural relaxations that increase basal spacing and decrease cohesion of the neighboring K-illite layers. We also provide evidence that the formation of alternating Cs- and K-illite interlayers (i.e., ordered interstratification) is both thermodynamically and mechanically favorable compared to exchange in adjacent interlayers.

Authors:
ORCiD logo [1];  [2]; ORCiD logo [3];  [3]
  1. Univ. of California, Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1532325
Alternate Identifier(s):
OSTI ID: 1421881
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 148; Journal Issue: 22; Journal ID: ISSN 0021-9606
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Schaettle, Karl, Ruiz Pestana, Luis, Head-Gordon, Teresa, and Lammers, Laura Nielsen. A structural coarse-grained model for clays using simple iterative Boltzmann inversion. United States: N. p., 2018. Web. doi:10.1063/1.5011817.
Schaettle, Karl, Ruiz Pestana, Luis, Head-Gordon, Teresa, & Lammers, Laura Nielsen. A structural coarse-grained model for clays using simple iterative Boltzmann inversion. United States. doi:10.1063/1.5011817.
Schaettle, Karl, Ruiz Pestana, Luis, Head-Gordon, Teresa, and Lammers, Laura Nielsen. Tue . "A structural coarse-grained model for clays using simple iterative Boltzmann inversion". United States. doi:10.1063/1.5011817. https://www.osti.gov/servlets/purl/1532325.
@article{osti_1532325,
title = {A structural coarse-grained model for clays using simple iterative Boltzmann inversion},
author = {Schaettle, Karl and Ruiz Pestana, Luis and Head-Gordon, Teresa and Lammers, Laura Nielsen},
abstractNote = {Cesium-137 is a crucial byproduct of nuclear energy generation and is environmentally threatening due to its long half-life and affinity for naturally occurring micaceous clays. Current experimental observations of illite and phlogopite mica indicate that Cs+ is capable of exchanging with K+ bound in the anhydrous interlayers of layered silicates, forming sharp exchange fronts, leading to interstratification of Cs- and K-illite. We introduce here a coarse-grained (CG) model of the anhydrous illite interlayer developed using iterative Boltzmann inversion that qualitatively and quantitatively reproduces features of a previously proposed feedback mechanism of ion exchange. The CG model represents a 70-fold speedup over all-atom models of clay systems and predicts interlayer expansion for K-illite near ion exchange fronts. Contrary to the longstanding theory that ion exchange in a neighboring layer increases the binding of K in lattice counterion sites leading to interstratification, we find that the presence of neighboring exchanged layers leads to short-range structural relaxations that increase basal spacing and decrease cohesion of the neighboring K-illite layers. We also provide evidence that the formation of alternating Cs- and K-illite interlayers (i.e., ordered interstratification) is both thermodynamically and mechanically favorable compared to exchange in adjacent interlayers.},
doi = {10.1063/1.5011817},
journal = {Journal of Chemical Physics},
number = 22,
volume = 148,
place = {United States},
year = {2018},
month = {2}
}

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Works referenced in this record:

A climbing image nudged elastic band method for finding saddle points and minimum energy paths
journal, December 2000

  • Henkelman, Graeme; Uberuaga, Blas P.; Jónsson, Hannes
  • The Journal of Chemical Physics, Vol. 113, Issue 22, p. 9901-9904
  • DOI: 10.1063/1.1329672