Extensive investigations on the boron chemistry in 1940s-1970s led to many important findings about basics of boron chemistry that continue to play key roles for the progresses in undersanding properties of boron allotropes and compounds in 21st century. This talk intends to make clear links between these basics of boron chemistry elucidated in early years and recent findings including role of frustration in boron allotropies where computational studies based on density functional theory (DFT) simulations played crucial roles. In boron allotropy, presence of icosahedron as a basic structural motif, as well as its incompativility with translational symmetry, has been known for quite long time. Nevertheless, it was only in the last decade that these structual properties and chemical properties lead to multitude of copeting effects, and one of which appears as geometrical frustration in beta-rhombohedral boron. This discovery prompted revisit of the old problem of alpha-tetragonal boron; thought to be once-resolved controversy as to whether a pure form of alpha-tetragonal phase could exist. The recent report suggested that a pure form of alpha-tetragonal boron (or something very similar) may in fact exist where partial occupancy combined with frustration induced by overconstraint may be at play. Also in the last decade, it was predicted that, one of stabilization mechanisms found for beta-boron, conversion of 2c-2e to 3c-2e bonds via interstitial, may also stabilize a pure form of 2D boron sheet. This theoretical prediction led to synthesis of 2D boron sheet on metal surfaces. Finally, I will discuss about potential roles of these fundamental chemical and physical factors in hydrogen charging and discharging processes for boron based hydrogen storage materials such as MgB2H8.

Chemistry of boron and physics of frustration in boron and boron compounds

254th National Meeting (2017)

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