Nanoparticle Structure by Coherent X-ray Diffraction

Abstract

This review examines the physical reasons why nanoparticles differ in structure from the bulk. Certain simple properties of nanoparticles are explained through these structural differences. A powerful method of measuring the three dimensional structure of nanoparticles, Coherent X-ray diffraction (CXD), is introduced. A key experiment is described that uses CXD to study the redistribution of strains on the surface of a Au nanocrystal. Some future perspectives are discussed in conclusion.

Anisotropic atom displacement in Pd nanocubes resolved by molecular dynamics simulations supported by x-ray diffraction imaging

“…However, the smallest nanocrystals which can be studied by CXD using currently available instruments are about 60nm in diameter. 26 Smaller crystalline sizes create considerable and still unsolved challenges in terms It may appear non-intuitive that the traditional and established technique of X-ray powder diffraction (XRPD) should enter the picture at this stage. Besides revealing the average phase composition, XRPD is routinely used to assess the size of nanocrystals: quick estimates are obtained from the peak width, exploiting the inverse proportionality with the domain size stated by the Scherrer equation, frequently ignoring effects of the specific nanocrystal shape, defects, and lattice distortions.…”

Coherent X-Ray Diffraction Imaging of Morphology and Strain in Nanomaterials

“…36 This phase transition is influenced by pressure and by particle size, which results in effective pressure. 37 The dielectric polarization, which results from oxygen ion displacements in the opposite direction from the Ba and Ti cations, is present in all phases. 38 A recent publication used x-ray powder diffraction analysis to infer a core-shell structure for the nanocrystalline BTO.…”

In situ strain evolution during a disconnection event in a battery nanoparticle

“…The phase retrieval code is adapted from published work 20,21 and augmented to include GPU capability. 90 iterations of the difference map algorithm 27 followed by ten iterations of the error reduction algorithm 28,29 were used and the algorithm converged after a total of 3150 iterations.…”

“…CXDI in Bragg geometry is a powerful tool that relies on synchrotron produced coherent Xrays and their diffraction from crystalline samples [14][15][16][17][18][19] . The 3D electron density and atomic displacement fields are retrievable from coherent diffraction patterns with the use of phase retrieval algorithms 20,21 . Strain fields are the derivatives of the 3D displacement field components.…”