2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 8: Composite & Ceramic, Quasi-crystals and Nanomaterials
| Editors: | Kongoli F, Pech-Canul M, Kalemtas A, Werheit H |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 300 pages |
| ISBN: | 978-1-987820-31-7 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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A Transdisciplinary Research for Boron Icosahedral Crystals and Aluminum-Based Icosahedral Quasicrystals
Kaoru Kimura1;1THE UNIVERSITY OF TOKYO, Chiba, Japan;
Type of Paper: Regular
Id Paper: 291
Topic: 18
Abstract:
We have constructed a unified picture for icosahedral cluster solids by a comparative transdisciplinary research for the boron (B) icosahedral crystals in the field of semiconductors and the aluminum (Al)-based icosahedral quasicrystals in the field of metals. For the icosahedral cluster of Al, metallic-covalent bonding conversion occurs whether the center atom exists or not. When the center is occupied or not by the atom, the packing fraction approaches to the closest packing structure or becomes very low, and the cluster has metallic or covalent bonding. On the other hand, there are no elements which can occupy the center of icosahedron of B, whereas the similar situation appears when an atom occupies the interstitial A1 site, which has the similar environment to the center of icosahedron, in beta-rhombohedral boron (beta-B). The metallic-covalent bonding conversion occurs by doping of vanadium, which has high occupancy of the A1 site. The beta-B is a self-compensated solid, where the electron deficient of B12 icosahedral and excess of B28 clusters are compensated by the interstitial atoms and vacancies, respectively. When electrons are doped by occupation of the interstitial site in beta-B by Li or Mg, the doped electrons are compensated initially by the decrease of the interstitial atoms and the increase of the vacancies, then by generation of vacancies in the new site. The beta-B is the only elemental crystal where the self-compensation occurs. In the case of V-doped beta-B, the doped V atoms drop out by Li or Mg doping, which is considered to be extended self-compensation. This phenomenon is also considered to be metallic-ionic bonding conversion. For the Al-based approximant crystals of icosahedral quasicrystal, the self-compensation occurs, where a number of vacancies increases by the electron doping induced by the constituent element substitution.