Title: A numerical method for deriving shape functions of nanoparticles for pair distribution function refinements

Abstract

We report that in the structural refinement of nanoparticles, discrete atomistic modeling can be used for small nanocrystals (< 15 nm), but becomes computationally unfeasible at larger sizes, where instead unit-cell-based small-box modeling is usually employed. However, the effect of the nanocrystal's shape is often ignored or accounted for with a spherical model regardless of the actual shape due to the complexities of solving and implementing accurate shape effects. Recent advancements have provided a way to determine the shape function directly from a pair distribution function calculated from a discrete atomistic model of any given shape, including both regular polyhedra (e.g. cubes, spheres, octahedra) and anisotropic shapes (e.g. rods, discs, ellipsoids) [Olds et al. (2015). J. Appl. Cryst. 48, 1651–1659], although this approach is still limited to small size regimes due to computational demands. In order to accurately account for the effects of nanoparticle size and shape in small-box refinements, a numerical or analytical description is needed. This article presents a methodology to derive numerical approximations of nanoparticle shape functions by fitting to a training set of known shape functions; the numerical approximations can then be employed on larger sizes yielding a more accurate and physically meaningful refined nanoparticle size.more » Lastly, the method is demonstrated on a series of simulated and real data sets, and a table of pre-calculated shape function expressions for a selection of common shapes is provided.« less

Authors:

Usher, Tedi-Marie  ^[1];

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• Search DOE PAGES for ORCID "0000-0001-8265-5972"
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Olds, Daniel P.  ^[1];

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Liu, Jue  ^[1];

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Page, Katharine L.  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-9071-3383"
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+ Show Author Affiliations

1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Neutron Scattering Division

Publication Date:

2018-06-06

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)

OSTI Identifier:

1474606

Grant/Contract Number:  

AC05-00OR22725; AC02-06CH11357

Resource Type:

Accepted Manuscript

Journal Name:

Acta Crystallographica. Section A, Foundations and Advances (Online)

Additional Journal Information:

Journal Name: Acta Crystallographica. Section A, Foundations and Advances (Online); Journal Volume: 74; Journal Issue: 4; Journal ID: ISSN 2053-2733

Publisher:

International Union of Crystallography

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; nanoparticles; shape function; pair distribution function; total scattering