2007 Fiscal Year Final Research Report Summary
Are higher order structures present in coordination-polyhedron structures of alloys, just like proteins?
| Project/Area Number |
18360306
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Waseda University |
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Principal Investigator |
KOYAMA Yasumasa Waseda University, Faculty of Science and Engineering, Professor (20150295)
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| Co-Investigator(Kenkyū-buntansha) |
HIROTSU Yoshihiko Osaka University, The Institute of Scientific and Industrial Research, Professor (70016525)
HIRATA Akihiko Osaka University, The Institute of Scientific and Industrial Research, Assistant Professor (90350488)
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| Project Period (FY) |
2006 – 2007
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| Keywords | coordination polyhedron / atomic column / nanometer-sized metastable state / higher order structure / hierarchy of crystal structures / covalent bond / transmission electron microscopy / intermetallic compound |
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| Research Abstract |
Coordination-polyhedron structures found in intermetallic compounds involving 3d-transition metals are characterized by the presence of complex coordination(CN) polyhedra such as a CN12 polyhedron. Because these polyhedra can be regarded as structural units, our motivation of this study is based on a simple question whether higher order structures are present in coordination-polyhedron structures or not, just as in the case of proteins. To get an answer of this question, in this study, we have tried to identify higher order structures in the g. and R structures of the Fe-Mo alloy system, where CN12, 14, 15, and 16 polyhedra are involved Concretely higher order structures in these two structures were determined on the basis of atomic arrangements of metastable states appearing in solid-state reactions from the bcc structures to them. The present experimental data obtained by transmission electron microscopy clearly revealed that there existed metastable states for both cases : the disordered atomic-column state and the short-range ordered state of atomic-column blocks in the μ case, and another disordered atomic-column state and the domain-structure state consisting of nanometer-sized atomic-column regions in the R case. Based on the appearance of these metastable states, we tried to determine higher order structures in the μ and R structures. As a result, four higher order structures related to a CN12 polyhedron are present in the structure, while there are two structures in the R structure, one of which is a CN16 polyhedron as a primary one. Thus the presence of these higher order structures in the μ and R structures is indicative of the fact that coordination-polyhedron structures in intermetallic compounds involving 3d-transition metals should have the hierarchy of crystal structures, which is directly associated with the formation and development of covalent bonds in a metallic system.
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