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Title: A Molecular Dynamics Investigation of Hydrolytic Polymerization in a Metal-Hydroxide Gel

Abstract

The early stages of the spontaneous hydrolytic polymerization of an active hydroxide in the anti-bayerite structure are followed by using molecular dynamics simulations. The polymer populations are calculated as a function of reaction progress and compared with a model governed by purely random bonding. In agreement with experimental observations in aqueous solutions, the transformation of singly bridged to doubly bridged metal ions is shown to have a significant autocatalytic component. The overall polymer populations, however, are very close to the predictions of the random bonding model, indicating that local autocatalytic behavior is decoupled from multimer populations at the larger scales. The calculations show that solid-state transformation processes do not preferentially give rise to higher order multimers, and suggest that interfacial processes, involving bulk solution, are required to facilitate rapid transformation to higher order oligomers. Two reaction pathways are identified for the dewatering of u-H3O2 bridges into u-OH bridges. Both are activated primarily by undercoordination of one of the metals centers involved in the bridge.

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
921592
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry B, 110(14):7107-7112; Journal Volume: 110; Journal Issue: 14
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AQUEOUS SOLUTIONS; METALS; HYDROXIDES; POLYMERIZATION; HYDROLYSIS; MOLECULAR DYNAMICS METHOD; WATER REMOVAL; Environmental Molecular Sciences Laboratory

Citation Formats

Rustad, James R., and Casey, William H.. A Molecular Dynamics Investigation of Hydrolytic Polymerization in a Metal-Hydroxide Gel. United States: N. p., 2006. Web. doi:10.1021/jp054379t.
Rustad, James R., & Casey, William H.. A Molecular Dynamics Investigation of Hydrolytic Polymerization in a Metal-Hydroxide Gel. United States. doi:10.1021/jp054379t.
Rustad, James R., and Casey, William H.. Thu . "A Molecular Dynamics Investigation of Hydrolytic Polymerization in a Metal-Hydroxide Gel". United States. doi:10.1021/jp054379t.
@article{osti_921592,
title = {A Molecular Dynamics Investigation of Hydrolytic Polymerization in a Metal-Hydroxide Gel},
author = {Rustad, James R. and Casey, William H.},
abstractNote = {The early stages of the spontaneous hydrolytic polymerization of an active hydroxide in the anti-bayerite structure are followed by using molecular dynamics simulations. The polymer populations are calculated as a function of reaction progress and compared with a model governed by purely random bonding. In agreement with experimental observations in aqueous solutions, the transformation of singly bridged to doubly bridged metal ions is shown to have a significant autocatalytic component. The overall polymer populations, however, are very close to the predictions of the random bonding model, indicating that local autocatalytic behavior is decoupled from multimer populations at the larger scales. The calculations show that solid-state transformation processes do not preferentially give rise to higher order multimers, and suggest that interfacial processes, involving bulk solution, are required to facilitate rapid transformation to higher order oligomers. Two reaction pathways are identified for the dewatering of u-H3O2 bridges into u-OH bridges. Both are activated primarily by undercoordination of one of the metals centers involved in the bridge.},
doi = {10.1021/jp054379t},
journal = {Journal of Physical Chemistry B, 110(14):7107-7112},
number = 14,
volume = 110,
place = {United States},
year = {Thu Apr 13 00:00:00 EDT 2006},
month = {Thu Apr 13 00:00:00 EDT 2006}
}