Three metallic BN polymorphs: 1D multi-threaded conduction in 3D network
In this paper, three new metallic sp2/sp3-hybridized Boron Nitride (BN) polymorphs are proposed by first-principles calculations. One of them named as tP-BN is predicted based on the evolutionary particle swarm structural search. tP-BN is constructed by two interlocked rings to form a tube-like 3D network. The stability and band structure calculations show tP-BN is metastable and metallic at zero pressure. Calculations of density of states and electron orbits confirm the metallicity is originate from the sp2-hybridized B and N atoms, and forming 1D linear conductive channel in its 3D network. According to the relations between atomic structure and electronic properties, another two 3D metastable metallic sp2/sp3-hybridized BN structures are constructed manually. Electronic properties calculations show both of them have 1D conductive channel along different axis. These polymorphs predicted in this study enrich the structures and gives a different picture in the conductive mechanism of BN compounds.