PHYSICS/BK21 SEMINAR (08/09/11)
관련링크
본문
"Ab initio structure determination from powder diffraction and Maximum entropy image reconstruction
연사: 허재혁 박사[미국표준기술연구소]
일시: 2008 년 9 월 11 일 15:00-16:00
장소: 물리학과 세미나실(3-201)
ABSTRACT:
The modern scientific understanding of materials starts on knowing their structures, where single crystal diffraction dominates. Many scientifically and/or practically interesting materials, however, often exist only as polycrystalline (powder) form. Fortunately, recent developments based on high resolution powder diffraction data allow one to solve rather complicated crystal structures. In this talk for instance, the structure solutions of molecular magnet and hydrogen storage materials are presented, which revealed unexpected features and provided natural explanations for previously observed ?but not understood ?experimental results. The molecular magnet system includes Fe(TCNE)2 y(solvent), the long-lasting problem, Fe(TCNE)(NCMe)2FeCl4 and (Fe(C5(CH3)5)2)(TCNE), etc. For the case of the hydrogen storage material, the novel metal organic framework MIL-53 (Al) structure was studied; revealing the rather complicated structural phase transition as a function of the temperature, gas loading pressure and adsorbed gas type. The second topic concerns a frequently met difficulty; how to treat the crystallographically poorly defined scattering densities which defy the conventional atomic model approaches. Maximum entropy method with Pawley fit makes best use of information contained in the X-ray powder diffraction pattern by considering the correlation between partially overlapped reflections.
문의처: 이기봉(054-279-2068, kibong@postech.ac.kr)
"
연사: 허재혁 박사[미국표준기술연구소]
일시: 2008 년 9 월 11 일 15:00-16:00
장소: 물리학과 세미나실(3-201)
ABSTRACT:
The modern scientific understanding of materials starts on knowing their structures, where single crystal diffraction dominates. Many scientifically and/or practically interesting materials, however, often exist only as polycrystalline (powder) form. Fortunately, recent developments based on high resolution powder diffraction data allow one to solve rather complicated crystal structures. In this talk for instance, the structure solutions of molecular magnet and hydrogen storage materials are presented, which revealed unexpected features and provided natural explanations for previously observed ?but not understood ?experimental results. The molecular magnet system includes Fe(TCNE)2 y(solvent), the long-lasting problem, Fe(TCNE)(NCMe)2FeCl4 and (Fe(C5(CH3)5)2)(TCNE), etc. For the case of the hydrogen storage material, the novel metal organic framework MIL-53 (Al) structure was studied; revealing the rather complicated structural phase transition as a function of the temperature, gas loading pressure and adsorbed gas type. The second topic concerns a frequently met difficulty; how to treat the crystallographically poorly defined scattering densities which defy the conventional atomic model approaches. Maximum entropy method with Pawley fit makes best use of information contained in the X-ray powder diffraction pattern by considering the correlation between partially overlapped reflections.
문의처: 이기봉(054-279-2068, kibong@postech.ac.kr)
"
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