2010 Fiscal Year Final Research Report

A first principles study of boron rich compounds with high mechanical properties in high temperature

Research Project

Project/Area Number	21760515
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Single-year Grants
Research Field	Physical properties of metals
Research Institution	Tohoku University
Principal Investigator	SAHARA Ryoji Tohoku University, 金属材料研究所, 助教 (30323075)
Project Period (FY)	2009 – 2010
Keywords	弾性特性 / ボロンリッチ化合物 / 第一原理計算 / モンテカルロ法
Research Abstract	We study first principles calculations on the bonding nature and metal (M) dependent changes in the atomic, electronic, and elastic properties of boron rich compounds such as AlMB_<14> (M=Li, Na and Mg) having B_<12> icosahedral clusters. These materials are candidates high mechanical properties in high temperatures. We found in all cases there is a strong bonding between the nearest neighbor boron atoms. A charge transfer from M atoms makes the boron atoms bridging the B12 icosahedra behave like carbon. These boron atoms form hexagonal rings between the neighboring icosahedra similar to the one found in the diamond structure in one direction leading to asymmetric bonding. Effects of addition of Si are also discussed.