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Toward a correct treatment of core properties with local hybrid functionals.
J Comput Chem
December 2023
Technische Universität Berlin, Institute of Chemistry Theoretical Chemistry/Quantum Chemistry, Berlin, Germany.
In local hybrid functionals (LHs), a local mixing function (LMF) determines the position-dependent exact-exchange admixture. We report new LHs that focus on an improvement of the LMF in the core region while retaining or partly improving upon the high accuracy in the valence region exhibited by the LH20t functional. The suggested new pt-LMFs are based on a Padé form and modify the previously used ratio between von Weizsäcker and Kohn-Sham local kinetic energies by different powers of the density to enable flexibly improved approximations to the correct high-density and iso-orbital limits relevant for the innermost core region.
View Article and Find Full Text PDFHigh-energy interference-free K-lines synchrotron X-ray fluorescence microscopy of rare earth elements in hyperaccumulator plants.
Metallomics
September 2023
Université de Lorraine, CNRS, LIEC, F-54000, Nancy, France.
Synchrotron-based micro-X-ray fluorescence analysis (µXRF) is a nondestructive and highly sensitive technique. However, element mapping of rare earth elements (REEs) under standard conditions requires care, since energy-dispersive detectors are not able to differentiate accurately between REEs L-shell X-ray emission lines overlapping with K-shell X-ray emission lines of common transition elements of high concentrations. We aim to test REE element mapping with high-energy interference-free excitation of the REE K-lines on hyperaccumulator plant tissues and compare with measurements with REE L-shell excitation at the microprobe experiment of beamline P06 (PETRA III, DESY).
View Article and Find Full Text PDFSimulating electron-excited energy dispersive X-ray spectra with the NIST DTSA-II open-source software platform.
MRS Adv
January 2022
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
NIST DTSA-II is a free, open access, and fully-documented comprehensive software platform for electron-excited X-ray microanalysis with energy dispersive spectrometry (EDS), including tools for quantification, measurement optimization, and spectrum simulation. EDS simulation utilizes a Monte Carlo electron trajectory simulation that includes characteristic and continuum X-ray generation, self-absorption, EDS window absorption, and energy-to-charge conversion leading to peak broadening. Spectra are simulated on an absolute basis considering electron dose and spectrometer parameters.
View Article and Find Full Text PDFDesign of a Multi-Monochromatic X-ray Imager (MMI) for Kr K-shell line emission.
Rev Sci Instrum
November 2022
Lawrence Livermore National Laboratories (LLNL), 7000 East Ave., Livermore, California 94550, USA.
The Multi-Monochromatic X-ray Imager (MMI) is a time-gated spectrometer used in implosion experiments at the OMEGA laser facility. From the data, electron temperature and density spatial distributions can be obtained at different implosion times. Previous MMI designs used Ar K-shell emission (3-6 keV) as a spectroscopic tracer and provided a spectral resolution of around 20 eV.
View Article and Find Full Text PDFEnergy-Dispersive X-Ray Spectrum Simulation with NIST DTSA-II: Comparing Simulated and Measured Electron-Excited Spectra.
Microsc Microanal
September 2022
National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Electron-excited X-ray microanalysis with energy-dispersive spectrometry (EDS) proceeds through the application of the software that extracts characteristic X-ray intensities and performs corrections for the physics of electron and X-ray interactions with matter to achieve quantitative elemental analysis. NIST DTSA-II is an open-access, fully documented, and freely available comprehensive software platform for EDS quantification, measurement optimization, and spectrum simulation. Spectrum simulation with DTSA-II enables the prediction of the EDS spectrum from any target composition for a specified electron dose and for the solid angle and window parameters of the EDS spectrometer.
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