Meeting room "Glova", 4 floor, Integrated Research Building
Abstract
Boron is one of the nonmetal elements which has been widely studied due to its complex polymorphism.Boron's three valence electrons are too localized to make it metallic and insufficient in number to form a simple covalent structure. As a result, boron atoms form B12 icosahedra linked together in a variety of ways. Only α- (rhombohedral, within a 12-atom unit cell) and β- (high temperature form, rhombohedral, structure is not fully understood and consists of 105 or 108 atoms in the unit cell) crystalline modifications of elemental boron are currently established as pure boron forms. Recently, Oganov et al. and Zarechnaya et al. independently synthesized a new form of boron at high pressure and high temperature. The new phase turned out to be a key to understanding the phase diagram of boron-the only element for which the phase diagram was unknown since its discovery 200 years ago. Here, we report the new pure boron (γ-boron, Orthorhombic, 28 atoms per unit cell) synthesized at pressures up to 18 GPa and temperatures up to ~2000 oC using a multianvil apparatus. In order to understand the phase diagram of boron, the P-T conditions of β- to γ-boron phase transition were also investigated under high pressure and high temperature using a multianvil apparatus combined with X-ray diffraction and Raman spectra.
For inquiry：Taku Tsuchiya TEL:（089）927-8198
E-mail takut@sci.ehime-u.ac.jp
