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SPring-8 Seminar (第230回)

副題/演題 Theoretical core-level spectroscopy
開催期間 2013年11月07日 (木) 10時00分から11時00分まで
開催場所 上坪講堂
主催 (公財)高輝度光科学研究センター(JASRI)
形式 レクチャー(講演)
概要

Speaker : Prof. Weine Olovsson

Language : ENGLISH

Affiliation : Theoretical Physics, Department of Physics, Chemistry and Biology (IFM), Linköping University, Sweden

Title : Theoretical core-level spectroscopy

Abstract :
By performing first-principles calculations for obtaining spectroscopic properties it is possible to investigate the electronic structure and bonding in a wide range of materials. Furthermore, the results can be used as a “fingerprint” in order to characterize different structures. In this presentation I will show different theoretical methodologies for core-level spectroscopy in comparison with experiment, for specific material studies.

Core-level binding energy shifts (CLSs) can be used as a sensitive probe of e.g. interface quality and intermixing of atoms. In substitutionally disordered alloys a so-called disorder broadening of the spectral core-line is expected due to the difference in the local chemical environment of the atoms. Also, one needs to consider lattice relaxation which can have a large effect in some systems. I will summarize some previous and new results focusing on disordered metallic alloys (e.g. AgPd) and interface systems (Ni/Cu/Ni) [1].

The most common methods to calculate the X-ray absorption near-edge structure (XANES) spectra are based on density functional theory (DFT) supercell techniques [2]. However, in order to carefully include the correlated motion of the core-hole and excited electron one needs to go beyond the single-particle picture. One way to do this is to use many-body perturbation theory by solving the Bethe-Salpeter equation (BSE). Here I will demonstrate results e.g. for the Li K-edge in Li-halides and Al L2,3-edge in different phases of AlN [3]. At present the BSE calculations are performed with the open source exciting-code [4].

It is a challenge to model amorphous structures and obtain representative XANES and extended x-ray absorption fine structure (EXAFS) spectra. Here I will demonstrate a computationally efficient way to do so with examples for Cr(1-x)C(x) surface alloys.

[1] W. Olovsson et al. J. Electron Spectroscopy Relat. Phenom. 178-9, 88 (2010)
[2] T. Mizoguchi et al. Micron 41, 695 (2010)
[3] W. Olovsson et al. Phys. Rev. B 83, 195206 (2011)
[4] http://exciting-code.org/

担当者 : 崔 芸涛
Mail : yitaocui@spring8.or.jp
PHS : 3758

問い合わせ先 JASRI 研究調整部 研究業務課 SPring-8セミナー事務局 垣口 伸二、吉川史津
0791-58-0949
0791-58-0830
spring8_seminar@spring8.or.jp
最終変更日 2015-05-07 13:31