TY - JOUR
T1 - Insights on the Alumina-Water Interface Structure by Direct Comparison of Density Functional Simulations with X-ray Reflectivity
AU - Harmon, Katherine J.
AU - Chen, Ying
AU - Bylaska, Eric J.
AU - Catalano, Jeffrey G.
AU - Bedzyk, Michael J.
AU - Weare, John H.
AU - Fenter, Paul
N1 - Funding Information:
This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences (DOE/BES) Division of Chemical Sciences, Geosciences, and Biosciences (Geosciences Research Program) through Argonne National Laboratory (ANL), the University of California San Diego, and Pacific Northwest National Laboratory. K.J.H. gratefully acknowledges support from the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program and from the Ryan Fellowship and the Northwestern University International Institute for Nanotechnology. J.G.C. was supported by the U.S. National Science Foundation (NSF) Environmental Chemical Sciences Program (Award No. CHE-1505532). Additional support from EMSL operations. EMSL operations are supported by the DOE’s Office of Biological and Environmental Research (Contract number DE-AC06-76RLO 1830). We wish to thank the Scientific Computing Staff, Office of Energy Research, and the U. S. Department of Energy for a grant of computer time at the National Energy Research Scientific Computing Center (Berkeley, CA). Some of the calculations were performed on the Cascade computing systems at the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL) at PNNL. X-ray reflectivity measurements were performed at beamline 33-ID-D of the Advanced Photon Source at ANL, a U.S. DOE Office of Science User Facility operated by ANL under Contract No. DE-AC02-06CH11357. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan. http://energy. gov/downloads/doe-public-accessplan.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2018/11/29
Y1 - 2018/11/29
N2 - Density functional theory molecular dynamics (DFT-MD) simulations are frequently used to predict the interfacial structures and dynamical processes at solid-water interfaces in efforts to gain a deeper understanding of these systems. However, the accuracy of these predictions has not been rigorously quantified. Here, direct comparisons between large-scale DFT-MD simulations and high-resolution X-ray reflectivity (XR) measurements of the well-defined Al2O3(001)/water interface reveal the relative accuracy of these two methods to describe interfacial structure, a comparison that is enabled by XR's high sensitivity to atomic-scale displacements. The DFT-MD simulated and XR model-fit structures are qualitatively similar, but XR signals calculated directly from the DFT-MD predictions deviate significantly from the experimental data, revealing discrepancies in these two approaches. Differences in the derived interfacial Al2O3 relaxation profiles of ∼0.02 Å within the top five layers are significant to XR, but at the limit of the accuracy of DFT. Further differences are found in the surface hydration layer with a simulated average water layer height ∼0.2 Å higher than that observed experimentally. This is outside the accuracy of both XR and DFT and is not improved by the inclusion of a phenomenological correction for hydrogen bonding (e.g., Grimme).
AB - Density functional theory molecular dynamics (DFT-MD) simulations are frequently used to predict the interfacial structures and dynamical processes at solid-water interfaces in efforts to gain a deeper understanding of these systems. However, the accuracy of these predictions has not been rigorously quantified. Here, direct comparisons between large-scale DFT-MD simulations and high-resolution X-ray reflectivity (XR) measurements of the well-defined Al2O3(001)/water interface reveal the relative accuracy of these two methods to describe interfacial structure, a comparison that is enabled by XR's high sensitivity to atomic-scale displacements. The DFT-MD simulated and XR model-fit structures are qualitatively similar, but XR signals calculated directly from the DFT-MD predictions deviate significantly from the experimental data, revealing discrepancies in these two approaches. Differences in the derived interfacial Al2O3 relaxation profiles of ∼0.02 Å within the top five layers are significant to XR, but at the limit of the accuracy of DFT. Further differences are found in the surface hydration layer with a simulated average water layer height ∼0.2 Å higher than that observed experimentally. This is outside the accuracy of both XR and DFT and is not improved by the inclusion of a phenomenological correction for hydrogen bonding (e.g., Grimme).
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U2 - 10.1021/acs.jpcc.8b08522
DO - 10.1021/acs.jpcc.8b08522
M3 - Article
AN - SCOPUS:85056202411
VL - 122
SP - 26934
EP - 26944
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 47
ER -