A new transferable tight-binding model for boron and its application to amorphous boron

Based on a transferable tight-binding model widely used for carbon, we develop a newly parameterized transferable tight-binding model for boron. Combined with molecular dynamics simulations, we study the energetics and structural properties of amorphous boron. We first optimize the α -rhombohedral boron structure, which is then heated above the melting point to obtain the liquid boron geometry. Starting from three different time frames, liquid boron is cooled down quickly to 300 K at three different cooling rates and therefore nine samples of amorphous boron are obtained. We analyze the samples and compare the results with some known properties of amorphous boron and available results of previous works. To further analyze the properties of amorphous boron, first principles calculations within the density functional theory (DFT) framework are used to study the electronic structure and local geometries. A finite but very small density of states at the Fermi level is observed after the DFT structural optimization. Based on geometrical analysis, we propose that besides the B ₁₂ icosahedron, a basic constituent unit of many boron phases, boron triangle chain is one of the main constituent units of amorphous boron.