ORCID Profile
0000-0002-4505-6898
Current Organisation
Aarhus University
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Publisher: International Union of Crystallography (IUCr)
Date: 2022
DOI: 10.1107/S2053273321011840
Abstract: Powder diffraction and pair distribution function (PDF) analysis are well established techniques for investigation of atomic configurations in crystalline materials, and the two are related by a Fourier transformation. In diffraction experiments, structural information, such as crystallite size and microstrain, is contained within the peak profile function of the diffraction peaks. However, the effects of the PXRD (powder X-ray diffraction) peak profile function on the PDF are not fully understood. Here, all the effects from a Voigt diffraction peak profile are solved analytically, and verified experimentally through a high-quality X-ray total scattering measurement on Ni powder. The Lorentzian contribution to the microstrain broadening is found to result in Voigt-shaped PDF peaks. Furthermore, it is demonstrated that an improper description of the Voigt shape during model refinement leads to overestimation of the atomic displacement parameter.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2018
DOI: 10.1007/S11739-018-1922-Y
Abstract: In the original publication, one of the ARAPACIS collaborators Dr. "Leonardo Di Gennaro" name has been erroneously mentioned as "Leonardo De Gennaro".
Publisher: International Union of Crystallography (IUCr)
Date: 2023
DOI: 10.1107/S2053273322010154
Abstract: The electron density and thermal motion of diamond are determined at nine temperatures between 100 K and 1000 K via synchrotron powder X-ray diffraction (PXRD) data collected on a high-accuracy detector system. Decoupling of the thermal motion from the thermally smeared electron density is performed via an iterative Wilson–Hansen–Coppens–Rietveld procedure using theoretical static structure factors from density functional theory (DFT) calculations. The thermal motion is found to be harmonic and isotropic in the explored temperature range, and excellent agreement is observed between experimental atomic displacement parameters (ADPs) and those obtained via theoretical harmonic phonon calculations (HPC), even at 1000 K. The Debye temperature of diamond is determined experimentally to be Θ D = 1883 (35) K. A topological analysis of the electron density explores the temperature dependency of the electron density at the bond critical point. The properties are found to be constant throughout the temperature range. The robustness of the electron density confirms the validity of the crystallographic convolution approximation for diamond in the explored temperature range.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0CY02307H
Abstract: Adding Fe to the PtPd nanocatalyst increases propene activity by forming more metallic Pt and PdO during synthesis and increasing Pt–Pd bond formation upon aging.
Publisher: International Union of Crystallography (IUCr)
Date: 2020
DOI: 10.1107/S205225251901580X
Abstract: The application of thermoelectrics for energy harvesting depends strongly on operational reliability and it is therefore desirable to investigate the structural integrity of materials under operating conditions. We have developed an operando setup capable of simultaneously measuring X-ray scattering data and electrical resistance on pellets subjected to electrical current. Here, operando investigations of β-Zn 4 Sb 3 are reported at current densities of 0.5, 1.14 and 2.3 A mm −2 . At 0.5 A mm −2 no s le decomposition is observed, but Rietveld refinements reveal increased zinc occupancy from the anode to the cathode demonstrating zinc migration under applied current. At 1.14 A mm −2 β-Zn 4 Sb 3 decomposes into ZnSb, but pair distribution function analysis shows that Zn 2 Sb 2 units are preserved during the decomposition. This identifies the mobile zinc in β-Zn 4 Sb 3 as the linkers between the Zn 2 Sb 2 units. At 2.3 A mm −2 severe Joule heating triggers transition into the γ-Zn 4 Sb 3 phase, which eventually decomposes into ZnSb, demonstrating Zn ion mobility also in γ-Zn 4 Sb 3 under electrical current.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9NR09069J
Abstract: Rutile TiO 2 nanocrystals are synthesized for the first time in a continuous flow hydrothermal process.
Publisher: International Union of Crystallography (IUCr)
Date: 30-06-2021
DOI: 10.1107/S2052252521005479
Abstract: Although crystalline solids are characterized by their periodic structures, some are only periodic on average and deviate on a local scale. Such disordered crystals with distinct local structures have unique properties arising from both collective and localized behaviour. Different local orderings can exist with identical average structures, making their differences hidden to Bragg diffraction methods. Using high-quality single-crystal X-ray diffuse scattering the local order in thermoelectric half-Heusler Nb 1− x CoSb is investigated, for which different local orderings are observed. It is shown that the vacancy distribution follows a vacancy repulsion model and the crystal composition is found always to be close to x = 1/6 irrespective of nominal s le composition. However, the specific synthesis method controls the local order and thereby the thermoelectric properties thus providing a new frontier for tuning material properties.
Publisher: International Union of Crystallography (IUCr)
Date: 06-03-2021
DOI: 10.1107/S2052252521001664
Abstract: Synchrotron powder X-ray diffraction (PXRD) is a well established technique for investigating the atomic arrangement of crystalline materials. At modern beamlines, X-ray scattering data can be collected in a total-scattering setting, which additionally opens up the opportunity for direct-space structural analysis through the atomic pair distribution function (PDF). Modelling of PXRD and PDF data is typically carried out separately, but employing a concurrent structural model to both direct- and reciprocal-space data has the possibility to enhance total-scattering data analysis. However, total-scattering measurements applicable to such dual-space analyses are technically demanding. Recently, the technical demands have been fulfilled by a MYTHEN microstrip detector system (OHGI), which meets the stringent requirements for both techniques with respect to Q range, Q resolution and dynamic range. In the present study, we evaluate the quality of total-scattering data obtained with OHGI by separate direct- and reciprocal-space analysis of Si. Excellent agreement between structural parameters in both spaces is found, demonstrating that the total-scattering data from OHGI can be utilized in dual-space structural analysis e.g. for in situ and operando measurements.
Publisher: Elsevier BV
Date: 03-2017
DOI: 10.1016/J.IJCARD.2017.01.001
Abstract: Vascular disease (VD), as assessed by history of myocardial infarction or peripheral artery disease or aortic plaque, increases stroke risk in atrial fibrillation (AF), and is a component of risk assessment using the CHA We analysed data from the ARAPACIS study, an observational study including 2027 Italian patients with non-valvular AF, in whom CP was detected using Doppler Ultrasonography. VD was reported in 351 (17.3%) patients while CP was detected in 16.6% patients. Adding CP to the VD definition leaded to higher VD prevalence (30.9%). During a median [IQR] follow-up time of 36months, 56 (2.8%) stroke/TIA events were recorded. Survival analysis showed that conventional VD alone did not increase the risk of stroke (Log-Rank: 0.009, p=0.924), while addition of CP to conventional VD was significantly associated to an increased risk of stroke (LR: 5.730, p=0.017). Cox regression analysis showed that VD+CP was independently associated with stroke (HR: 1.78, 95% CI: 1.05-3.01, p=0.0318). Reclassification analysis showed that VD+CP allowed a significant risk reclassification when compared to VD alone in predicting stroke at 36months (NRI: 0.192, 95% CI: 0.028-0.323, p=0.032). In non-valvular AF patients the addition of ultrasound detection of carotid plaque to conventional VD significantly increases the predictive value of CHA
No related grants have been discovered for Jonas Beyer.