TY - JOUR
T1 - Water Interactions with Nanoporous Silica
T2 - Comparison of ReaxFF and ab Initio based Molecular Dynamics Simulations
AU - Rimsza, J. M.
AU - Yeon, Jejoon
AU - Van Duin, A. C.T.
AU - Du, Jincheng
N1 - Funding Information:
This work is supported by the US Department of Energy (DOE) Nuclear Energy University Project (Project No. 13-5494) and National Science Foundation (NSF) DMR Ceramics Program (Project No. 1508001). J.M.R. acknowledges that this material is based on work supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. DGE-114248. Computational resources are provided by the University of North Texas high performance computing cluster.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/11/3
Y1 - 2016/11/3
N2 - Detailed understanding of the reactions and processes which govern silicate-water interactions is critical to geological, materials, and environmental sciences. Interactions between water and nanoporous silica were studied using classical molecular dynamics with a Reactive Force Field (ReaxFF), and the results were compared with density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations. Two versions of ReaxFF Si/O/H parametrizations (Yeon et al. J. Phys. Chem. C 2016, 120, 305 and Fogarty et al. J. Chem. Phys. 2010, 132, 174704) were compared with AIMD results to identify differences in local structures, water dissociation mechanisms, energy barriers, and diffusion behaviors. Results identified reaction mechanisms consisting of two different intermediate structures involved in the removal of high energy two-membered ring (2-Ring) defects on complex nanoporous silica surfaces. Intermediate defects lifetimes affect hydroxylation and 2-Ring defect removal. Additionally, the limited internal volume of the nanoporous silica results in decreased water diffusion related to the development of nanoconfined water. Hydrogen atoms in the water diffused 10-30% faster than the oxygen atoms, suggesting that increased hydrogen diffusion through hydrogen hopping mechanisms may be enhanced in nanoconfined conditions. Comparison of the two different ReaxFF parametrizations with AIMD data indicated that the Yeon et al. parameters resulted in reaction mechanisms, hydroxylation rates, defect concentrations, and activation energies more consistent with the AIMD simulations. Therefore, this ReaxFF parametrization is recommended for future studies of water-silica systems with high concentrations of surface defects and highly strained siloxane bonds such as in complex silica nanostructures.
AB - Detailed understanding of the reactions and processes which govern silicate-water interactions is critical to geological, materials, and environmental sciences. Interactions between water and nanoporous silica were studied using classical molecular dynamics with a Reactive Force Field (ReaxFF), and the results were compared with density functional theory (DFT) based ab initio molecular dynamics (AIMD) simulations. Two versions of ReaxFF Si/O/H parametrizations (Yeon et al. J. Phys. Chem. C 2016, 120, 305 and Fogarty et al. J. Chem. Phys. 2010, 132, 174704) were compared with AIMD results to identify differences in local structures, water dissociation mechanisms, energy barriers, and diffusion behaviors. Results identified reaction mechanisms consisting of two different intermediate structures involved in the removal of high energy two-membered ring (2-Ring) defects on complex nanoporous silica surfaces. Intermediate defects lifetimes affect hydroxylation and 2-Ring defect removal. Additionally, the limited internal volume of the nanoporous silica results in decreased water diffusion related to the development of nanoconfined water. Hydrogen atoms in the water diffused 10-30% faster than the oxygen atoms, suggesting that increased hydrogen diffusion through hydrogen hopping mechanisms may be enhanced in nanoconfined conditions. Comparison of the two different ReaxFF parametrizations with AIMD data indicated that the Yeon et al. parameters resulted in reaction mechanisms, hydroxylation rates, defect concentrations, and activation energies more consistent with the AIMD simulations. Therefore, this ReaxFF parametrization is recommended for future studies of water-silica systems with high concentrations of surface defects and highly strained siloxane bonds such as in complex silica nanostructures.
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U2 - 10.1021/acs.jpcc.6b07939
DO - 10.1021/acs.jpcc.6b07939
M3 - Article
AN - SCOPUS:84994764974
VL - 120
SP - 24803
EP - 24816
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 43
ER -