اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدCrystal structure solution from experimentally determined atomic pair distribution functions
64
0
0.0
(
0
)
تأليف
Pavol Juhas
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The paper describes an extension of the Liga algorithm for structure solution from atomic pair distribution function (PDF), to handle periodic crystal structures with multiple elements in the unit cell. The procedure is performed in 2 separate steps - at first the Liga algorithm is used to find unit cell sites consistent with pair distances extracted from the experimental PDF. In the second step the assignment of atom species over cell sites is solved by minimizing the overlap of their empirical atomic radii. The procedure has been demonstrated on synchrotron x-ray PDF data from 16 test samples. The structure solution was successful for 14 samples including cases with enlarged super cells. The algorithm success rate and the reasons for failed cases are discussed together with enhancements that should improve its convergence and usability.
قيم البحث
اقرأ أيضاً
Many crystalline materials show chemical short range order and relaxation of neighboring atoms. Local structural information can be obtained by analyzing the atomic pair distribution function (PDF) obtained from powder diffraction data. In this paper
, we present the successful extraction of chemical short range order parameters from the x-ray PDF of a quenched Cu_3Au sample.
A new approach is presented to obtain candidate structures from atomic pair distribution function (PDF) data in a highly automated way. It fetches, from web-based structural databases, all the structures meeting the experimenters search criteria and
performs structure refinements on them without human intervention. It supports both x-ray and neutron PDFs. Tests on various material systems show the effectiveness and robustness of the algorithm in finding the correct atomic crystal structure. It works on crystalline and nanocrystalline materials including complex oxide nanoparticles and nanowires, low-symmetry and locally distorted structures, and complicated doped and magnetic materials. This approach could greatly reduce the traditional structure searching work and enable the possibility of high-throughput real-time auto analysis PDF experiments in the future.
We have experimentally elucidated the correlation between inverse and direct Edelstein Effects (EEs) at Bi2O3/Cu interface by means of spin absorption method using lateral spin valve structure. The conversion coefficient {lambda} for the inverse EE i
s determined by the electron momentum scattering time in the interface, whereas the coefficient q for the direct EE is by the spin ejection time from the interface. For the Bi2O3/Cu interface, the spin ejection time was estimated to be ~ 53 fs and the momentum scattering time ~ 13 fs at room temperature, both of which contribute to the total momentum relaxation time that defines the resistivity of the interface. The effective spin Hall angle for the Bi2O3/Cu interface amounts to ~ 10% which is comparable to commonly used spin Hall material such as platinum. Interesting to note is that the experimentally obtained Edelstein resistances given by the output voltage divided by the injection current for direct and inverse effects are the same. Analysis based on our phenomenological model reveals that the larger the momentum scattering time, the more efficient direct EE; and the smaller spin ejection time, the more efficient inverse EE.
High resolution total and indium differential atomic pair distribution functions (PDFs) for In_(0.5)Ga_(0.5)As alloys have been obtained by high energy and anomalous x-ray diffraction experiments, respectively. The first peak in the total PDF is reso
lved as a doublet due to the presence of two distinct bond lengths, In-As and Ga-As. The In differential PDF, which involves only atomic pairs containing In, yields chemical specific information and helps ease the structure data interpretation. Both PDFs have been fit with structure models and the way in that the underlying cubic zinc-blende lattice of In_(0.5)Ga_(0.5)As semiconductor alloy distorts locally to accommodate the distinct In-As and Ga-As bond lengths present has been quantified.
The frequency distributions of sizes and fluxes of supra-arcade downflows (SADs) provide information about the process of their creation. For example, a fractal creation process may be expected to yield a power-law distribution of sizes and/or fluxes
. We examine 120 cross-sectional areas and magnetic flux estimates found by Savage & McKenzie for SADs, and find that (1) the areas are consistent with a log-normal distribution and (2) the fluxes are consistent with both a log-normal and an exponential distribution. Neither set of measurements is compatible with a power-law distribution nor a normal distribution. As a demonstration of the applicability of these findings to improved understanding of reconnection, we consider a simple SAD growth scenario with minimal assumptions, capable of producing a log-normal distribution.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
