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Title: Visualising the molecular alteration of the calcite (104) – water interface by sodium nitrate

Authors:
; ; ; ;  [1];  [2];  [2]
  1. Karlsruher
  2. (
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
FOREIGN
OSTI Identifier:
1239408
Resource Type:
Journal Article
Resource Relation:
Journal Name: Scientific Reports; Journal Volume: 6; Journal Issue: 2016
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Hofmann, Sascha, Voitchovsky, Kislon, Spijker, Peter, Schmidt, Moritz, Stumpf, Thorsten, Durham), and Aalto). Visualising the molecular alteration of the calcite (104) – water interface by sodium nitrate. United States: N. p., 2016. Web. doi:10.1038/srep21576.
Hofmann, Sascha, Voitchovsky, Kislon, Spijker, Peter, Schmidt, Moritz, Stumpf, Thorsten, Durham), & Aalto). Visualising the molecular alteration of the calcite (104) – water interface by sodium nitrate. United States. doi:10.1038/srep21576.
Hofmann, Sascha, Voitchovsky, Kislon, Spijker, Peter, Schmidt, Moritz, Stumpf, Thorsten, Durham), and Aalto). 2016. "Visualising the molecular alteration of the calcite (104) – water interface by sodium nitrate". United States. doi:10.1038/srep21576.
@article{osti_1239408,
title = {Visualising the molecular alteration of the calcite (104) – water interface by sodium nitrate},
author = {Hofmann, Sascha and Voitchovsky, Kislon and Spijker, Peter and Schmidt, Moritz and Stumpf, Thorsten and Durham) and Aalto)},
abstractNote = {},
doi = {10.1038/srep21576},
journal = {Scientific Reports},
number = 2016,
volume = 6,
place = {United States},
year = 2016,
month = 6
}
  • New insights into the structure of the calcite-water interface are obtained through direct model-independent comparison of multiple classical molecular dynamics (MD) simulations with high-resolution specular X-ray reflectivity (XR) data. This set of comparisons, with four different state-of-the-art force fields (including two non-polarizable, one polarizable, and one reactive force field), reveal new insights into the absolute accuracy of the simulated structures and the uniqueness of the XR-derived structural results. These four simulations, while qualitatively similar, have visibly distinct interfacial structure, and are distinguished through a quantitative comparison of the XR signals calculated from these simulations with experimental XR data. The resultsmore » demonstrate that the simulated calcite-water interface structures, as a whole, are not consistent with the XR data (i.e., within their precision and accuracy). This disagreement is largely due to the simulation of the calcite lattice. The simulated interfacial water profiles show substantially different levels of agreement with the XR data. Of these, the rigid-ion model (RIM) simulations show the best consistency with the experimental XR data. Further model-dependent comparisons of the structural parameters that describe the interfacial structure (derived from both the MD simulations and the XR data) provide further insight into the sources of differences between these two approaches. Using the new insights from the RIM simulations, new structures of the calcite-water interface consistent with both the experimental data and the simulation are identified and compared to recent results.« less
  • Molecular dynamics simulations have been used to investigate the behavior of aqueous sodium nitrate in interfacial environments. Polarizable potentials for the water molecules and the nitrate ion in solution were employed. Calculated surface tension data at several concentrations are in good agreement with measured surface tension data. The surface potential of NaNO3 solutions at two concentrations also compare favorably with experimental measurements. Density profiles suggest that NO3 - resides primarily below the surface of the solutions over a wide range of concentrations. When the nitrate anions approach the surface of the solution, they are significantly undercoordinated compared to in themore » bulk, and this may be important for reactions where solvent cage effects play a role, such as photochemical processes. Surface water orientation is perturbed by the presence of nitrate ions, and this has implications for experimental studies that probe interfacial water orientation. Nitrate ions near the surface also have a preferred orientation that places the oxygen atoms in the plane of the interface. The availability of NO3 - for reaction at the surface of aerosols in the atmosphere is discussed. The work at Pacific Northwest National Laboratory was performed under the auspices of the Division of Chemical Sciences, Office of Basic Energy Sciences, U.S. Department of Energy. Pacific Northwest National Laboratory is operated by Battelle for the Department of Energy.« less
  • Synchrotron X-ray scattering measurements were performed in situ during the formation of thin (50-600 {Angstrom}) overgrowths of otavite-calcite solid-solutions at the (1014) cleavage surface of single- crystal calcite. These solid-solutions were precipitated from EDTA-bearing aqueous solutions having varied initial saturation states of otavite and calcite. From repetitive X-ray diffraction scans, the Cd/(Ca + Cd) ratios and the effective thicknesses (average domain size perpendicular to the calcite cleavage surface) of the solid-solutions were determined as a function of time. Additional in-plane X-ray diffraction scans were done to further characterize the relationship between the solid-solutions and the calcite cleavage surface. The solid-solutionmore » phase grew epitaxially with a (1014) growth plane oriented parallel to the calcite (1014) cleavage surface. The compositions of the solid-solutions evolved with time, while their growth rates (increases in effective thickness) remained fairly constant (10-54 {Angstrom}/hr). In each experiment, the coverage of the initial surface by the solid-solution (calculated from the difference between the initial and final Cd concentrations in the aqueous solution) was about 20%. Glancing-incidence X-ray reflectivity scans were also monitored as a function of time. From these scans, we determined that the solid-water interface did not become significantly rougher during the nucleation and growth of the solid-solution phase. These observations indicate that the solid-solution grew by layer spreading and that most growth may have occurred preferentially at macrostep faces produced during cleavage. 30 refs., 6 figs., 2 tabs.« less