The amount of data collected during synchrotron X-ray diffraction (XRD) experiments is constantly increasing. Most of the time, the data are collected with image detectors, which necessitates the use of image reduction/integration routines to extract structural information from measured XRD patterns. This step turns out to be a bottleneck in the data processing procedure due to a lack of suitable software packages. In particular, fast-running synchrotron experiments require online data reduction and analysis in real time so that experimental parameters can be adjusted interactively. Dioptas is a Python-based program for on-the-fly data processing and exploration of two-dimensional X-ray diffraction area detector data, specifically designed for the large amount of data collected at XRD beamlines at synchrotrons. Its fast data reduction algorithm and graphical data exploration capabilities make it ideal for online data processing during XRD experiments and batch post-processing of large numbers of images.

DIOPTAS: a program for reduction of two-dimensional X-ray diffraction data and data exploration

Nickel-rich layered lithium transition metal oxides have been investigated as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost. Such an oxide with high capacity (215 mA h g-1), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle, is now proposed. Nickel-rich layered lithium transition-metal oxides, LiNi1−xMxO2 (M = transition metal), have been under intense investigation as high-energy cathode materials for rechargeable lithium batteries because of their high specific capacity and relatively low cost1,2,3. However, the commercial deployment of nickel-rich oxides has been severely hindered by their intrinsic poor thermal stability at the fully charged state and insufficient cycle life, especially at elevated temperatures1,2,3,4,5,6. Here, we report a nickel-rich lithium transition-metal oxide with a very high capacity (215 mA h g−1), where the nickel concentration decreases linearly whereas the manganese concentration increases linearly from the centre to the outer layer of each particle. Using this nano-functional full-gradient approach, we are able to harness the high energy density of the nickel-rich core and the high thermal stability and long life of the manganese-rich outer layers. Moreover, the micrometre-size secondary particles of this cathode material are composed of aligned needle-like nanosize primary particles, resulting in a high rate capability. The experimental results suggest that this nano-functional full-gradient cathode material is promising for applications that require high energy, long calendar life and excellent abuse tolerance such as electric vehicles.

/pdf/nanostructured-high-energy-cathode-materials-for-advanced-207wu2d02c.pdf

Nanostructured high-energy cathode materials for advanced lithium batteries

Three of the fundamental catalytic limitations that have plagued the electrochemical production of hydrogen for decades still remain: low efficiency, short lifetime of catalysts and a lack of low-cost materials. Here, we address these three challenges by establishing and exploring an intimate functional link between the reactivity and stability of crystalline (CoS2 and MoS2) and amorphous (CoSx and MoSx) hydrogen evolution catalysts. We propose that Co(2+) and Mo(4+) centres promote the initial discharge of water (alkaline solutions) or hydronium ions (acid solutions). We establish that although CoSx materials are more active than MoSx they are also less stable, suggesting that the active sites are defects formed after dissolution of Co and Mo cations. By combining the higher activity of CoSx building blocks with the higher stability of MoSx units into a compact and robust CoMoSx chalcogel structure, we are able to design a low-cost alternative to noble metal catalysts for efficient electrocatalytic production of hydrogen in both alkaline and acidic environments.

Design of active and stable Co-Mo-Sx chalcogels as pH-universal catalysts for the hydrogen evolution reaction.

PDFgetX3 is a new software application for converting X-ray powder diffraction data to an atomic pair distribution function (PDF). PDFgetX3 has been designed for ease of use, speed and automated operation. The software can readily process hundreds of X-ray patterns within a few seconds and is thus useful for high-throughput PDF studies that measure numerous data sets as a function of time, temperature or other environmental parameters. In comparison to the preceding programs, PDFgetX3 requires fewer inputs and less user experience and it can be readily adopted by novice users. The live-plotting interactive feature allows the user to assess the effects of calculation parameters and select their optimum values. PDFgetX3 uses an ad hoc data correction method, where the slowly changing structure-independent signal is filtered out to obtain coherent X-ray intensities that contain structure informa­tion. The output from PDFgetX3 has been verified by processing experimental PDFs from inorganic, organic and nanosized samples and comparing them with their counterparts from a previous established software. In spite of the different algorithm, the obtained PDFs were nearly identical and yielded highly similar results when used in structure refinement. PDFgetX3 is written in the Python language and features a well documented reusable code base. The software can be used either as a standalone application or as a library of PDF processing functions that can be called from other Python scripts. The software is free for open academic research but requires paid license for commercial use.

http://slapper.apam.columbia.edu/bib/papers/13juhasjac.pdf

PDFgetX3: a rapid and highly automatable program for processing powder diffraction data into total scattering pair distribution functions

Compression versus pressure at ambient temperature has been measured for tantalum, gold, and platinum to $94\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and for aluminum, copper, and tungsten to $153\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, in a diamond anvil cell. Standard synchrotron x-ray diffraction accuracy in the volume determination could be achieved to the maximum pressure. The current data set is used to recalibrate the static pressure scale based on the ruby luminescence, confirming recent suggestions of an underestimation of pressure. Using an updated pressure calibration, the consistency between ultrasonic, dynamic, and static measurements of the equations of state is improved for these six equations of state. This consistency allows us to test the predictive power of density functional theory, with different approximations, for equation-of-state calculations. For example, the generalized gradient approximation leads to very accurate results, except for gold, the heaviest element.

Equations of state of six metals above 94 GPa

Detector systems introduce distortions into acquired data. To obtain accurate angle and intensity information, it is necessary to calibrate, and apply corrections. Intensity non-linearity, spatial distortion, and non-uniformity of intensity response, are the primary considerations. It is better to account for the distortions within scientific analysis software, but often it is more practical to correct the distortions to produce ‘idealised’ data. Calibration methods and software have been developed for single crystal diffraction experiments, using both approaches. For powder diffraction experiments the additional task of converting a two-dimensional image to a one-dimensional spectrum is used to allow Rietveld analysis. This task may be combined with distortion correction to produce intensity information and error estimates. High-pressure experiments can introduce additional complications and place new demands on software. Flexibility is needed to be able to integrate different angular regions se...

D. Hausermann

Papers

Two-dimensional detector software: From real detector to idealised image or two-theta scan