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Ytterbium doping in all-inorganic lead-halide perovskites [CsPb(Cl1−xBrx )3] generates interesting properties including quantum cutting and narrow line emission, making these materials attractive spectral down converters for solar photovoltaics. The relationship between this optical efficiency and the defect structure(s) associated with Yb3+ dopants within perovskites is not well understood. Various charge-neutral doping motifs have previously been proposed and studied computationally, including clusters involving two substitutional Yb3+ ions charge compensated by a single local Pb2+ vacancy. Near-band-edge defect states associated with such motifs are believed to play an important mechanistic role in quantum cutting itself. Here, we report the results of x-ray absorption and x-ray total-scattering measurements on ytterbium-doped CsPbCl3. XANES shows that the dopant oxidation state is exclusively Yb3+, and a combination of Yb L3 and Pb L3 extended x-ray absorption fine structure (EXAFS) shows that this Yb3+ substitutes exclusively at Pb2+ sites, where it adopts a pseudo-octahedral [YbCl6] 3− coordination environment. Shell-by-shell fits to the data show a short Yb-Cl bond distance of 2.58 Å compared to the Pb-Cl bond distance of 2.83 Å. We confirm this finding by x-ray pair distribution function analysis, which also shows evidence of additional Pb2+ vacancy formation induced by Yb3+ doping. We evaluate whether this is the primary mechanism of charge compensation using simulated EXAFS and pair distribution function data for several computed defect structures. Together, these results resolve the local dopant structures and charge-compensation mechanisms in lanthanide-doped all-inorganic lead-halide perovskites, and, as such, significantly advance the understanding of structure-function relationships in this important class of materials.

We present a new processing & analysis package of the atomic pair distribution function (PDF) for the electron diffraction (ED) pattern based on the total scattering theory which has been broadly used in the X-ray or neutron diffraction to reveal the local atomic structures, but PDF analysis based on the electron diffraction is still rarely used for the lack of an efficient PDF tool. The program was written as a package of DigitalMicrograph, a very popular software to record and analyze the data of transmission electron microscopes (TEM) in the most of TEM laboratories. The azimuthal rotation-average projection algorithm was implemented to enhance the signal-noise ratio of the intensity profile. In order to obtain the reduced structure function, the cubic spline fitting method was utilized to subtract the background scattering. The real-time displayed PDF makes data normalization easier and more accurate, and results of coordination numbers and averaged bond angles can be extracted from calibrated PDFs in real time. Program summary Program Title: ePDF tools Program Files doi: http://dx.doi.org/10.17632/ff94wp42wd.1 Licensing provisions: GPLv3 Programming language: DigitalMicrograph scripting language Nature of problem: The total scattering technique has been widely used in X-ray or neutron diffraction, but for the electron diffraction it still lacks an efficient analysis tool for the atomic pair distribution function. Solution method: Intensity profile is obtained by azimuthal rotation-average projection of 2D SAED pattern, the background scattering is subtracted by the cubic spline method, data normalization is real-time performed based on the total scattering theory, the atomic pair distribution functions obtained by Fourier transform will be used to quantitative analysis.

High-energy X-ray scattering and pair distribution function analysis (HEXS/PDF) is a powerful method to reveal the structure of materials lacking long-range order, but is underutilized for molecular complexes in solution. Here we demonstrate the application of HEXS/PDF with 0.26 A resolution to uncover the solution structure of five bimetallic Os(II)/Ru(II)/Cu(I) complexes. HEXS/PDF of each complex in acetonitrile solution confirms the pairwise interactions in the local coordination sphere of each metal center as well as the metal···metal interactions separated by over 12 A. The metal···metal distance detected in solution is compared with that from the crystal structure and molecular models to confirm that distortions to the metal bridging ligand are unique to the solid state. This work presents the first example of observing sub-A conformational difference by direct comparison of solution phase and solid-state structures and shows the potential for HEXS/PDF in the determination of solution structure of single molecules.

Atomic pair distribution function (PDF) analysis has been widely used to investigate nanocrystalline and structurally disordered materials. Experimental PDFs retrieved from electron diffraction (eP...

The mechanism research of structure-related reactions on Li2MnO3 is important to enhance the electrochemical performance of lithium-manganese-rich layered oxides. Although there are some reports on the structure evolution of Li2MnO3 during cycling process, the employed research techniques are very limited, mainly in/ex-situ X-ray diffraction, X-ray absorption and transmission electron microscopy. Here, atomic pair distribution function, a method to study the local atomic arrangement on the basis of average spectroscopic information, is used for the first time to study the local structure evolution of Li2MnO3 during electrochemical charge/discharge cycles. The results clearly demonstrate that Mn3+/Mn4+ redox couple is activated and Mn ions are reduced during discharging process. Some Mn ions in Mn layers can significantly migrate to Li layers and occupy the octahedral sites. As a result, a portion of inserted Li ions can occupy the face-shared tetrahedron sites, accompanied by the formation of local spinel-like structure. This work provides an important and suitable method based on the average spectroscopic information to investigate the local structure of electrode materials of lithium-ion batteries as well as other advanced battery systems.

A new web platform is presented for the pair distribution function (PDF) community to use and share advanced PDF analysis software in the cloud., A cloud web platform for analysis and interpretation of atomic pair distribution function (PDF) data (PDFitc) is described. The platform is able to host applications for PDF analysis to help researchers study the local and nanoscale structure of nanostructured materials. The applications are designed to be powerful and easy to use and can, and will, be extended over time through community adoption and development. The currently available PDF analysis applications, structureMining, spacegroupMining and similarity­Mapping, are described. In the first and second the user uploads a single PDF and the application returns a list of best-fit candidate structures, and the most likely space group of the underlying structure, respectively. In the third, the user can upload a set of measured or calculated PDFs and the application returns a matrix of Pearson correlations, allowing assessment of the similarity between different data sets. structureMining is presented here as an example to show the easy-to-use workflow on PDFitc. In the future, as well as using the PDFitc applications for data analysis, it is hoped that the community will contribute their own codes and software to the platform.

Made available in DSpace on 2018-12-11T16:49:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-09-01 This work reports the setting up of the X-ray diffraction and spectroscopy beamline at the Brazilian Synchrotron Light Laboratory for performing total scattering experiments to be analyzed by atomic pair distribution function (PDF) studies. The results of a PDF refinement for Al2O3 standard are presented and compared with data acquired at a beamline of the Advanced Photon Source, where it is common to perform this type of experiment. A preliminary characterization of the Pb1-xLaxZr0.40Ti0.60O3 ferroelectric system, with x = 0.11, 0.12 and 0.15, is also shown.A setup for total scattering experiments at the multi-purpose XDS beamline of the Brazilian Synchrotron Light Laboratory (LNLS) is described. Also, a preliminary characterization of the Pb1-xLaxZr0.40Ti0.60O3 (x = 0.11, 0.12 and 0.15) ferroelectric system using pair distribution function analysis is presented. Instituto de Física 'Gleb Wataghin' Universidade de Campinas (UNICAMP) Laboratório Nacional de Luz Síncrotron, Caixa Postal 6192 Instituto Geociências and Ciências Exatas Universidade Estadual Paulista (UNESP) Instituto de Física de São Carlos Universidade de São Paulo, CP 369 CONICET - Centro Atómico Bariloche CNEA Instituto Geociências and Ciências Exatas Universidade Estadual Paulista (UNESP)

Agradecimentos: The authors acknowledge the LNLS (XRD1-16082 and XRD1-16982) and APS (GUP-40487) for the beam time. We thank the staff of the XDS and the 11-ID-B beamlines, especially Dr Karena Chapman and Dr Olaf Borkiewicz (APS) for the measurement of the alumina standard at APS. Also, the authors are grateful to Professor Dr Valeri Petkov for fruitful discussions and Dr Frederico Alves-Lima for assitance during the measurement at the XDS beamline. This work was supported by FAPESP (Processes 2013/02160-5 and 2012/04870-7) and CNPq, Brazil Abstract: This work reports the setting up of the X-ray diffraction and spectroscopy beamline at the Brazilian Synchrotron Light Laboratory for performing total scattering experiments to be analyzed by atomic pair distribution function (PDF) studies. The results of a PDF refinement for Al2O3 standard are presented and compared with data acquired at a beamline of the Advanced Photon Source, where it is common to perform this type of experiment. A preliminary characterization of the Pb1-xLaxZr0.40Ti0.60O3 ferroelectric system,with x = 0.11, 0.12 and 0.15, is also shown FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ Fechado

A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented., A novel approach for finding and evaluating structural models of small metallic nanoparticles is presented. Rather than fitting a single model with many degrees of freedom, libraries of clusters from multiple structural motifs are built algorithmically and individually refined against experimental pair distribution functions. Each cluster fit is highly constrained. The approach, called cluster-mining, returns all candidate structure models that are consistent with the data as measured by a goodness of fit. It is highly automated, easy to use, and yields models that are more physically realistic and result in better agreement to the data than models based on cubic close-packed crystallographic cores, often reported in the literature for metallic nanoparticles.