scholarly journals Predicting short-range order and correlated phenomena in disordered crystalline materials

2020 ◽  
Vol 6 (35) ◽  
pp. eabc2758 ◽  
Author(s):  
Eric C. O’Quinn ◽  
Kurt E. Sickafus ◽  
Rodney C. Ewing ◽  
Gianguido Baldinozzi ◽  
Joerg C. Neuefeind ◽  
...  
Keyword(s):  
Short Range ◽  
Atomic Scale ◽  
Crystalline Materials ◽  
Radiation Fields ◽  
Straightforward Application ◽  
Structural Distortions ◽  
The Impact ◽  
Disordered Crystalline Materials ◽  
Structural Disordering ◽  
Intense Radiation

Disordered crystalline materials are used in a wide variety of energy-related technologies. Recent results from neutron total scattering experiments have shown that the atomic arrangements of many disordered crystalline materials are not random nor are they represented by the long-range structure observed from diffraction experiments. Despite the importance of disordered materials and the impact of disorder on the expression of physical properties, the underlying fundamental atomic-scale rules of disordering are not currently well understood. Here, we report that heterogeneous disordering (and associated structural distortions) can be understood by the straightforward application of Pauling’s rules (1929). This insight, corroborated by first principles calculations, can be used to predict the short-range, atomic-scale changes that result from structural disordering induced by extreme conditions associated with energy-related applications, such as high temperature, high pressure, and intense radiation fields.

Atomic resolution characterisation of interface structures by Electron Energy Loss Spectroscopy

1993 ◽  
Vol 51 ◽  
pp. 576-577
Author(s):  
N. D. Browning ◽  
M. M. McGibbon ◽  
M. F. Chisholm ◽  
S. J. Pennycook
Keyword(s):  
High Resolution ◽  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Imaging Technique ◽  
Atomic Scale ◽  
Atomic Resolution ◽  
Reference Image ◽  
The Impact ◽  
Electron Energy Loss

The recent development of the Z-contrast imaging technique for the VG HB501 UX dedicated STEM, has added a high-resolution imaging facility to a microscope used mainly for microanalysis. This imaging technique not only provides a high-resolution reference image, but as it can be performed simultaneously with electron energy loss spectroscopy (EELS), can be used to position the electron probe at the atomic scale. The spatial resolution of both the image and the energy loss spectrum can be identical, and in principle limited only by the 2.2 Å probe size of the microscope. There now exists, therefore, the possibility to perform chemical analysis of materials on the scale of single atomic columns or planes.In order to achieve atomic resolution energy loss spectroscopy, the range over which a fast electron can cause a particular excitation event, must be less than the interatomic spacing. This range is described classically by the impact parameter, b, which ranges from ~10 Å for the low loss region of the spectrum to <1Å for the core losses.

scholarly journals Dynamic lattice distortions driven by surface trapping in semiconductor nanocrystals

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Burak Guzelturk ◽  
Benjamin L. Cotts ◽  
Dipti Jasrasaria ◽  
John P. Philbin ◽  
David A. Hanifi ◽  
...  
Keyword(s):  
Photon Energy ◽  
Semiconductor Nanocrystals ◽  
Atomic Scale ◽  
Atomistic Simulations ◽  
Shell System ◽  
Structural Distortions ◽  
Colloidal Semiconductor Nanocrystals ◽  
Femtosecond Electron Diffraction ◽  
Structural Deformations ◽  
Nonradiative Processes

AbstractNonradiative processes limit optoelectronic functionality of nanocrystals and curb their device performance. Nevertheless, the dynamic structural origins of nonradiative relaxations in such materials are not understood. Here, femtosecond electron diffraction measurements corroborated by atomistic simulations uncover transient lattice deformations accompanying radiationless electronic processes in colloidal semiconductor nanocrystals. Investigation of the excitation energy dependence in a core/shell system shows that hot carriers created by a photon energy considerably larger than the bandgap induce structural distortions at nanocrystal surfaces on few picosecond timescales associated with the localization of trapped holes. On the other hand, carriers created by a photon energy close to the bandgap of the core in the same system result in transient lattice heating that occurs on a much longer 200 picosecond timescale, dominated by an Auger heating mechanism. Elucidation of the structural deformations associated with the surface trapping of hot holes provides atomic-scale insights into the mechanisms deteriorating optoelectronic performance and a pathway towards minimizing these losses in nanocrystal devices.

scholarly journals Atomic Migration Studies with X-Ray Photon Correlation Spectroscopy

2014 ◽  
Vol 2 ◽  
pp. 73-94 ◽  
Author(s):  
Markus Stana ◽  
Manuel Ross ◽  
Bogdan Sepiol
Keyword(s):  
Low Temperatures ◽  
Short Range ◽  
Short Range Order ◽  
Photon Correlation Spectroscopy ◽  
Condensed Matter ◽  
Correlation Spectroscopy ◽  
Atomic Scale ◽  
Photon Correlation ◽  
X Ray ◽  
Amorphous Systems

The new technique of atomic-scale X-ray Photon Correlation Spectroscopy (aXPCS) makesuse of a coherent X-ray beam to study the dynamics of various processes in condensed matter systems.Particularly atomistic migration mechanisms are still far from being understood in most of intermetallicalloys and in amorphous systems. Special emphasis must be given to the opportunity to measureatomistic diffusion at relatively low temperatures where such measurements were far out of reach withpreviously established methods. The importance of short-range order is demonstrated on the basis ofMonte Carlo simulations.

Sensitivity Analysis and Experimental Validation of Transient Performance Predictions for a Short-Range Turbofan

2016 ◽  
Author(s):  
Maria V. Culmone ◽  
Nicolás Garcia-Rosa ◽  
Xavier Carbonneau
Keyword(s):  
Short Range ◽  
Engine Performance ◽  
Sensitivity Study ◽  
Simulation Software ◽  
Tip Clearance ◽  
Mass Storage ◽  
Transient Effects ◽  
Transient Model ◽  
Blade Tip ◽  
The Impact

Transient effects are important features of engine performance calculations. The aim of this paper is to analyze a new, fully transient model implemented using the PRopulsion Object Oriented Simulation Software (PROOSIS) for a civil, short range turbofan engine. A transient turbofan model, including the mechanical inertia effect has been developed in PROOSIS. Specific physical effects such as heat soakage, mass storage, blade tip clearance and combustion delay have been implemented in the relevant components of PROOSIS to obtain a fully transient model. Since a large number of components are concerned by all the transient effects, an influence study is presented to determine which are the most critical effects, and in which components. Inertia represents the relevant phenomenon, followed by thermal effects, combustion delay and finally mass storage. The comparison with experimental data will provide a first validation of the model. Finally a sensitivity study is reported to assess the impact of uncertain knowledge of key input parameters in the response time prediction accuracy.

scholarly journals Designing order–disorder transformation in high-entropy ferritic steels

2021 ◽  
Author(s):  
Prashant Singh ◽  
Duane D. Johnson
Keyword(s):  
Short Range ◽  
Density Functional ◽  
Short Range Order ◽  
Range Order ◽  
Atomic Scale ◽  
Atomic Fraction ◽  
Compositional Variation ◽  
Ferritic Steels ◽  
Chemical Inhomogeneity ◽  
High Entropy

AbstractOrder–disorder transformations hold an essential place in chemically complex high-entropy ferritic steels (HEFSs) due to their critical technological application. The chemical inhomogeneity arising from mixing of multi-principal elements of varying chemistry can drive property altering changes at the atomic scale, in particular short-range order. Using density-functional theory-based linear-response theory, we predict the effect of compositional tuning on the order–disorder transformation in ferritic steels—focusing on Cr–Ni–Al–Ti–Fe HEFSs. We show that Ti content in Cr–Ni–Al–Ti–Fe solid solutions can be tuned to modify short-range order that changes the order–disorder path from BCC-B2 (Ti atomic-fraction = 0) to BCC-B2-L21 (Ti atomic-fraction > 0) consistent with existing experiments. Our study suggests that tuning degree of SRO through compositional variation can be used as an effective means to optimize phase selection in technologically useful alloys. Graphic abstract

Radiance Preprocessing for Assimilation in the Hourly Updating Rapid Refresh Mesoscale Model: A Study Using AIRS Data

2017 ◽  
Vol 32 (5) ◽  
pp. 1781-1800 ◽  
Author(s):  
Haidao Lin ◽  
Stephen S. Weygandt ◽  
Agnes H. N. Lim ◽  
Ming Hu ◽  
John M. Brown ◽  
...  
Keyword(s):  
Bias Correction ◽  
Short Range ◽  
Mesoscale Model ◽  
Channel Selection ◽  
Atmospheric Temperature ◽  
Study Data ◽  
Satellite Systems ◽  
Initial Application ◽  
Radiance Data ◽  
The Impact

Abstract This study describes the initial application of radiance bias correction and channel selection in the hourly updated Rapid Refresh model. For this initial application, data from the Atmospheric Infrared Sounder (AIRS) are used; this dataset gives atmospheric temperature and water vapor information at higher vertical resolution and accuracy than previously launched low-spectral resolution satellite systems. In this preliminary study, data from AIRS are shown to add skill to short-range weather forecasts over a relatively data-rich area. Two 1-month retrospective runs were conducted to evaluate the impact of assimilating clear-sky AIRS radiance data on 1–12-h forecasts using a research version of the National Oceanic and Atmospheric Administration (NOAA) Rapid Refresh (RAP) regional mesoscale model already assimilating conventional and other radiance [AMSU-A, Microwave Humidity Sounder (MHS), HIRS-4] data. Prior to performing the assimilation, a channel selection and bias-correction spinup procedure was conducted that was appropriate for the RAP configuration. RAP forecasts initialized from analyses with and without AIRS data were verified against radiosonde, surface atmosphere, precipitation, and satellite radiance observations. Results show that the impact from AIRS radiance data on short-range forecast skill in the RAP system is small but positive and statistically significant at the 95% confidence level. The RAP-specific channel selection and bias correction procedures described in this study were the basis for similar applications to other radiance datasets now assimilated in version 3 of RAP implemented at NOAA’s National Centers for Environmental Prediction (NCEP) in August 2016.

scholarly journals The impact of anion ordering on octahedra distortion and phase transitions in SrTaO2N and BaTaO2N

2017 ◽  
Vol 73 (3) ◽  
pp. 389-398 ◽  
Author(s):  
Chun-Hai Wang ◽  
Brendan J. Kennedy ◽  
André L. Menezes de Oliveira ◽  
Julia Polt ◽  
Kevin Steven Knight
Keyword(s):  
Solid State Reaction Method ◽  
Unit Cell ◽  
Site Preference ◽  
Structural Distortions ◽  
Distortion Analysis ◽  
Oxygen Anions ◽  
Four Square ◽  
A Site ◽  
The Impact ◽  
The Ideal

In this work we synthesized BaTaO2N and SrTaO2N using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaO2N [P4/mmm(No. 123)] and SrTaO2N [I4/mcm(No. 140)]. In contrast to an anion-disordered cubic perovskite (Pm \overline{3}m No. 221) with Ta at the cell center, both systems show a site preference for oxygen anions in the two opposite corners (along thecaxis) of the Ta–O/N octahedra rather than the four square corners in theabplane (Γ3+occupancy distortion), which induces a tetragonal elongation of the unit cell with thecaxis being longer than theaaxis. A further Ta–O/N octahedra displacement [R5−(a,0,0), rotation about thecaxis] distortion was observed in SrTaO2N. This distortion mode is accompanied by an increased unit-cell distortion that decreases as the temperature increases. Ultimately a second-order phase transition caused by the loss of theR5−(a,0,0) mode was observed at 400–450 K.

Measuring the deformation of crystalline materials due to the impact of eroding particles

Wear ◽  
1995 ◽  
Vol 181-183 ◽  
pp. 790-798
Author(s):  
C Henning
Keyword(s):  
Crystalline Materials ◽  
The Impact
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