skip to main content

DOE PAGESDOE PAGES

Title: Precise determination of water exchanges on a mineral surface

Solvent exchanges on solid surfaces and dissolved ions are a fundamental property important for understanding chemical reactions, but the rates of fast exchanges are poorly constrained. In this paper, we probed the diffusional motions of water adsorbed onto nanoparticles of the mineral barite (BaSO 4) using quasi-elastic neutron scattering (QENS) and classical molecular dynamics (MD) to reveal the complex dynamics of water exchange along mineral surfaces. QENS data as a function of temperature and momentum transfer (Q) were fit using scattering functions derived from MD trajectories. The simulations reproduce the dynamics measured in the experiments at ambient temperatures, but as temperature is lowered the simulations overestimate slower motions. Decomposition of the MD-computed QENS intensity into contributions from adsorbed and unbound water shows that the majority of the signal arises from adsorbed species, although the dynamics of unbound water cannot be dismissed. The mean residence times of water on each of the four surface sites present on the barite {001} were calculated using MD: at room temperature the low barium site is 194 ps, whereas the high barium site contains two distributions of motions at 84 and 2.5 ps. These contrast to 13 ps residence time on both sulfate sites, withmore » an additional surface diffusion exchange of 66 ps. Surface exchanges are similar to those of the aqueous ions calculated using the same force field: Ba aq 2+ is 208 ps and SO 4aq 2- is 5.8 ps. Finally, this work demonstrates how MD can be a reliable method to deconvolute solvent exchange reactions when quantitatively validated by QENS measurements.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [5] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Data Analysis and Visualization Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). UTK/ORNL Shull Wollan Center
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). UTK/ORNL Joint Inst. for Computational Sciences
Publication Date:
Grant/Contract Number:
AC05-00OR22725; FWP-3ERKCSNL
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 41; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; barite; water exchange; quasi-elastic neutron scattering; molecular dynamics; aqueous barium ion; aqueous sulfate ion
OSTI Identifier:
1339391

Stack, Andrew G., Borreguero, Jose M., Prisk, Timothy R., Mamontov, Eugene, Wang, Hsiu-Wen, Vlcek, Lukas, and Wesolowski, David J.. Precise determination of water exchanges on a mineral surface. United States: N. p., Web. doi:10.1039/C6CP05836A.
Stack, Andrew G., Borreguero, Jose M., Prisk, Timothy R., Mamontov, Eugene, Wang, Hsiu-Wen, Vlcek, Lukas, & Wesolowski, David J.. Precise determination of water exchanges on a mineral surface. United States. doi:10.1039/C6CP05836A.
Stack, Andrew G., Borreguero, Jose M., Prisk, Timothy R., Mamontov, Eugene, Wang, Hsiu-Wen, Vlcek, Lukas, and Wesolowski, David J.. 2016. "Precise determination of water exchanges on a mineral surface". United States. doi:10.1039/C6CP05836A. https://www.osti.gov/servlets/purl/1339391.
@article{osti_1339391,
title = {Precise determination of water exchanges on a mineral surface},
author = {Stack, Andrew G. and Borreguero, Jose M. and Prisk, Timothy R. and Mamontov, Eugene and Wang, Hsiu-Wen and Vlcek, Lukas and Wesolowski, David J.},
abstractNote = {Solvent exchanges on solid surfaces and dissolved ions are a fundamental property important for understanding chemical reactions, but the rates of fast exchanges are poorly constrained. In this paper, we probed the diffusional motions of water adsorbed onto nanoparticles of the mineral barite (BaSO4) using quasi-elastic neutron scattering (QENS) and classical molecular dynamics (MD) to reveal the complex dynamics of water exchange along mineral surfaces. QENS data as a function of temperature and momentum transfer (Q) were fit using scattering functions derived from MD trajectories. The simulations reproduce the dynamics measured in the experiments at ambient temperatures, but as temperature is lowered the simulations overestimate slower motions. Decomposition of the MD-computed QENS intensity into contributions from adsorbed and unbound water shows that the majority of the signal arises from adsorbed species, although the dynamics of unbound water cannot be dismissed. The mean residence times of water on each of the four surface sites present on the barite {001} were calculated using MD: at room temperature the low barium site is 194 ps, whereas the high barium site contains two distributions of motions at 84 and 2.5 ps. These contrast to 13 ps residence time on both sulfate sites, with an additional surface diffusion exchange of 66 ps. Surface exchanges are similar to those of the aqueous ions calculated using the same force field: Baaq2+ is 208 ps and SO4aq2- is 5.8 ps. Finally, this work demonstrates how MD can be a reliable method to deconvolute solvent exchange reactions when quantitatively validated by QENS measurements.},
doi = {10.1039/C6CP05836A},
journal = {Physical Chemistry Chemical Physics. PCCP (Print)},
number = 41,
volume = 18,
place = {United States},
year = {2016},
month = {10}
}