• Open Access

Validating first-principles molecular dynamics calculations of oxide/water interfaces with x-ray reflectivity data

Katherine J. Harmon, Kendra Letchworth-Weaver, Alex P. Gaiduk, Federico Giberti, Francois Gygi, Maria K. Y. Chan, Paul Fenter, and Giulia Galli
Phys. Rev. Materials 4, 113805 – Published 16 November 2020
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Abstract

Metal oxide/water interfaces play a crucial role in many electrochemical and photocatalytic processes, such as photoelectrochemical water splitting, the creation of fuel from sunlight, and electrochemical CO2 reduction. First-principles electronic structure calculations can reveal unique insights into these processes, such as the role of the alignment of the oxide electronic energy levels with those of liquid water. An essential prerequisite for the success of such calculations is the ability to predict accurate structural models of these interfaces, which in turn requires careful experimental validation. Here we report a general, quantitative validation protocol for first-principles molecular dynamics simulations of oxide/aqueous interfaces. The approach makes direct comparisons of interfacial x-ray reflectivity (XR) signals from experimental measurements and those obtained from ab initio simulations with semilocal and van der Waals functionals. The protocol is demonstrated here for the case of the Al2O3(001)/water interface, one of the simplest oxide/water interfaces. We discuss the technical requirements needed for validation, including the choice of the density functional, the simulation cell size, and the optimal choice of the thermodynamic ensemble. Our results establish a general paradigm for the validation of structural models and interactions at solid/water interfaces derived from first-principles simulations. While there is qualitative agreement between the simulated structures and the experimental best-fit structure, direct comparisons of simulated and measured XR intensities show quantitative discrepancies that derive from both bulk regions (i.e., alumina and water) as well as the interfacial region, highlighting the need for accurate density functionals to properly describe interfacial interactions. Our results show that XR data are sensitive not only to the atomic structure (i.e., the atom locations) but also to the electron-density distributions in both the substrate and at the interface.

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  • Received 30 June 2020
  • Revised 16 October 2020
  • Accepted 22 October 2020

DOI:https://doi.org/10.1103/PhysRevMaterials.4.113805

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsInterdisciplinary Physics

Authors & Affiliations

Katherine J. Harmon1,*, Kendra Letchworth-Weaver2,3,4,*, Alex P. Gaiduk3, Federico Giberti3, Francois Gygi5, Maria K. Y. Chan2, Paul Fenter6, and Giulia Galli3,7,8,†

  • 1Applied Physics Graduate Program, Northwestern University, Evanston, Illinois 60208, USA
  • 2Center for Nanoscale Materials, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 3Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA
  • 4Department of Physics and Astronomy, James Madison University, Harrisonburg, Virginia, 22807, USA
  • 5Department of Computer Science, University of California, Davis, California 95616, USA
  • 6Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 7Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
  • 8Department of Chemistry, University of Chicago, Chicago, Illinois 60637, USA

  • *These authors contributed equally to this work.
  • Author to whom correspondence should be addressed: gagalli@uchicago.edu

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Issue

Vol. 4, Iss. 11 — November 2020

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