Simon J. L. Billinge

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Emerging complex functional materials often have atomic order limited to the nanoscale. Examples include nanoparticles, species encapsulated in mesoporous hosts, and bulk crystals with intrinsic nanoscale order. The powerful methods that we have for solving the atomic structure of bulk crystals fail for such materials. Currently, no broadly applicable,(More)
We report the structure of methylammonium lead(II) iodide perovskite in mesoporous TiO2, as used in high-performance solar cells. Pair distribution function analysis of X-ray scattering reveals a two component nanostructure: one component with medium range crystalline order (30 atom %) and another with only local structural coherence (70 atom %). The(More)
Studying the structure of disordered and partially ordered materials is notoriously difficult. Recently, significant advances have been made using the atomic pair distribution function (PDF) analysis of powder diffraction data coupled with the use of advanced X-ray and neutron sources and fast computers. Here we summarize some of the more spectacular(More)
An image plate (IP) detector coupled with high energy synchrotron radiation was used for atomic pair distribution function (PDF) analysis, with high probed momentum transfer Q max ≤ 28.5 ˚ A −1 from crystalline materials. Materials with different structural complexities were measured to test the validity of the quantitative data analysis. Experimental(More)
We report the observation of local structural dipoles that emerge from an undistorted ground state on warming, in contrast to conventional structural phase transitions in which distortions emerge on cooling. Using experimental and theoretical probes of the local structure, we demonstrate this behavior in binary lead chalcogenides, which were believed to(More)
The program PDFFIT is designed for the full pro®le structural re®nement of the atomic pair distribution function (PDF). In contrast to conventional structure re®nement based on Bragg intensities, the PDF probes the local structure of the studied material. The program presented here allows the re®nement of atomic positions, anisotropic thermal parameters and(More)
Advances in materials science and molecular biology followed rapidly from the ability to characterize atomic structure using single crystals. Structure determination is more difficult if single crystals are not available. Many complex inorganic materials that are of interest in nanotechnology have no periodic long-range order and so their structures cannot(More)
The relationship between the equations used in the atomic pair distribution function (PDF) method and those commonly used in small-angle-scattering (SAS) analyses is explicitly shown. The origin of the sloping baseline, -4pirrho0, in PDFs of bulk materials is identified as originating from the SAS intensity that is neglected in PDF measurements. The(More)