Kimura group (Nano-space Function Design Group)
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TEL: +81-(0)4-7136-5456 FAX: +81-(0)4-7136-3758
e-mail: bkimura@phys.mm.t.u-tokyo.ac.jp |
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| We found that icosahedral clusters of boron and aluminum have metallic or covalent bonds depending on the existence of a central atom in the cluster, and proposed a concept of "metallic-covalent bondingconversion". On the other hand, the symmetry of the icosahedral cluster cannot coexist with the periodicity of the crystal. In boron- and aluminum-based compounds composed of icosahedral clusters, there are several phases which extend continuously from metal to semiconductor and from crystal to quasicrystal. These compounds are rich in variety and are expected to yield new functional materials. We joined these two groups ofmaterials to be one group of icosahedral cluster solids, and are trying to construct a unified picture by analyzing the structures, investigating the electronic states using molecular orbital calculations, obtaining the electron density distribution using the MEM/Reitvelt method and measuring the electrical, optical and thermal properties. We are developing new functional materials taking advantage of the characteristics of icosahedral cluster solids, i.e., thermoelectric material and highly resistive chip material using the intermediateproperties between a metal and a semiconductor, and a superconducting material using the high symmetry of the icosahedron. 
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