Low-dimensional boron structures based on icosahedron B-12

摘要

One-dimensional icosahedral boron chains and two-dimensional icosahedral boron sheets (icosahedral alpha, delta(6), and delta(4) sheets) that contain icosahedra B-12 as their building units have been predicted in a computer simulation study using a state-of-the-art semi-empirical Hamiltonian. These novel low-dimensional icosahedral structures exhibit interesting bonding and electronic properties. Specifically, the three-center, two-electron bonding between icosahedra B-12 of the boron bulk (rhombohedral boron) transforms into a two-center bonding in these new allotropes of boron sheets. In contrast to the previously reported stable buckled a and triangular boron monolayer sheets, these new allotropes of boron sheets form a planar network. Calculations of electronic density of states (DOS) reveal a semiconducting nature for both the icosahedral chain and the icosahedral delta(6) and delta(4) sheets, as well as a nearly gapless (or metallic-like) feature in the DOS for the icosahedral alpha sheet. The results for the energy barrier per atom between the icosahedral delta(6) and alpha sheets (0.17 eV), the icosahedral delta(6) and delta(4) sheets (0.38 eV), and the icosahedral alpha and delta(4) sheets (0.27 eV), as indicated in the respective parentheses, suggest that these new allotropes of boron sheets are relatively stable.