Geometries and Electronic Structures of Boron Clusters: Planar Structures and All-boron Fullerenes

Boron by itself and in combination with other elements can form a variety of atomic clusters. These clusters can be categorized into pure boron clusters, boron-hydrogen mixtures, called boranes (or borohydrides), boron-carbon-hydrogen mixtures, called carboranes, and boron-transition metal mixtures, called metallacarboranes. Because of their peculiar structures and unusual chemical bonding, boron clusters yield a variety of applications in different areas, such as coordination polymers[1], liquid crystals [2], ionic liquids [3], luminescent materials [4], and medicine [5]. Thus, they attract the interests of interdisciplinary researchers. A primary task in the research of boron clusters is to find the most stable structures of clusters containing given numbers and types of atoms. In this mini-review, we summarize the geometries and electronic structures of two commonly studied boron clusters, planar boron clusters and all-boron fullerenes.