Search results for "reverse Monte Carlo"
showing 10 items of 32 documents
Al driven peculiarities of local coordination and magnetic properties in single phase Alx CrFeCoNi high entropy alloys
2021
The authors thank the Helmholtz-Zentrum Berlin for the provision of access to synchrotron radiation facilities and allocation of synchrotron radiation at the PM2-VEKMAG, BAMline, and UE46_PGM-1 beamlines of BESSY II at HZB as well as measurement time for magnetometry at HZB CoreLab for Quantum Materials. A. S. acknowledges personal funding from CALIPSOplus project (the Grant Agreement no. 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020). The financial support for the VEKMAG project and the PM2-VEKMAG beamline by the German Federal Ministry for Education and Research (Nos. BMBF 05K10PC2, 05K10WR1, 05K10KE1) and by HZB is cordially acknowledged by all co-author…
Local structure of copper nitride revealed by EXAFS spectroscopy and a reverse Monte Carlo/evolutionary algorithm approach
2016
Physica scripta 91(5), 054003 (2016). doi:10.1088/0031-8949/91/5/054003
Molecular dynamics and reverse Monte Carlo modeling of scheelite-type AWO4(A = Ca, Sr, Ba) WL3-edge EXAFS spectra
2016
Classical molecular dynamics (MD) and reverse Monte Carlo methods coupled with ab initio multiple-scattering extended x-ray absorption fine structure (EXAFS) calculations were used for modeling of scheelite-type AWO4 (A = Ca, Sr, Ba) W L 3-edge EXAFS spectra. The two theoretical approaches are complementary and allowed us to perform analysis of full EXAFS spectra. Both methods reproduce well the structure and dynamics of tungstates in the outer coordination shells, however the classical MD simulations underestimate the W–O bond MSRD due to a neglect of quantum zero-point-motion. The thermal vibration amplitudes, correlation effects and anisotropy of the tungstate structure were also estimat…
Local Structure of Multiferroic MnWO4 and Mn0.7Co0.3WO4 Revealed by the Evolutionary Algorithm
2015
A novel reverse Monte Carlo/evolutionary algorithm scheme was applied to the analysis of the W L3-edge and Mn(Co) K-edges EXAFS spectra from multiferroic MnWO4 and Mn0.7Co0.3WO4. A 3D structural model, consistent with the experimental data, was obtained, and the influence of composition and temperature on the local structure of tungstates is discussed.
Reverse Monte Carlo modeling of thermal disorder in crystalline materials from EXAFS spectra
2012
Abstract In this work we present the Reverse Monte Carlo (RMC) modeling scheme, designed to probe the local structural and thermal disorder in crystalline materials by fitting the wavelet transform (WT) of the EXAFS signal. Application of the method to the analysis of the Ge K-edge and Re L3-edge EXAFS signals in crystalline germanium and rhenium trioxide, respectively, is presented with special attention to the problem of thermal disorder and related phenomena.
Analysis of extended x-ray absorption fine structure data from copper tungstate by the reverse Monte Carlo method
2014
The static disorder and lattice dynamics of crystalline materials can be efficiently studied using reverse Monte Carlo simulations of extended x-ray absorption fine structure spectra (EXAFS). In this work we demonstrate the potentiality of this method on an example of copper tungstate CuWO4. The simultaneous analysis of the Cu K and W L3 edges EXAFS spectra allowed us to follow local structure distortion as a function of temperature.
High-temperature X-ray absorption spectroscopy study of thermochromic copper molybdate
2019
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/5 and SJZ/2018/1 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The work was also supported by philanthropist MikroTik and administrated by the University of Latvia Foundation . The experiment at the Elettra synchrotron was performed within the project No. 20150303 .
Evidence of nickel ions dimerization in NiWO4 and NiWO4-ZnWO4 solid solutions probed by EXAFS spectroscopy and reverse Monte Carlo simulations
2021
Abstract The existence of exchange-coupled Ni 2 + ions – the so-called magnetic dimers – in wolframite-type NiWO 4 and Zn c Ni 1 − c WO 4 solid solutions with high nickel content was discovered by X-ray absorption spectroscopy combined with reverse Monte Carlo (RMC) simulations. Temperature- (10–300 K) and composition-dependent X-ray absorption spectra were measured at the Ni K-edge, Zn K-edge, and W L 3 -edge of microcrystalline NiWO 4 , Zn c Ni 1 − c WO 4 and ZnWO 4 . Structural models were obtained from simultaneous analysis of the extended X-ray absorption fine structure (EXAFS) spectra at three metal absorption edges using RMC simulations. The obtained radial distribution functions for…
Temperature dependence of the local structure and lattice dynamics of wurtzite-type ZnO
2014
Temperature-dependent (10–300 K) Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra of polycrystalline wurtzitetype ZnO were analyzed using ab initio multiple-scattering theory and taking into account anisotropy of the crystallographic structure and thermal disorder. We employed two different simulation approaches: classical molecular dynamics (MD) and reverse Monte Carlo coupled with an evolutionary algorithm (RMC/EA method). The accuracy of several force-field models, which are commonly used in the MD simulations of bulk and nanostructured ZnO, was tested based on a comparison between the experimental and simulated Zn K-edge EXAFS spectra. It was found that available force…
Thermal disorder and correlation effects in anti-perovskite-type copper nitride
2017
This work has been supported by the Latvian National Research Program IMIS2. The EXAFS experiment has been financed from the European Community's Seventh Framework Programme under grant agreement No. 226716 (Project I-20100098 EC). J.T. also gratefully acknowledges support from the National Science Foundation under the DMREF program Grant No. CHE-1534184.