title: Graphene-like Two-Dimensional Ionic Boron with Double Dirac Cones at Ambient Condition.
abstract: Recently, partially ionic boron (γ-B28) has been predicted and observed in pure boron, in bulk phase and controlled by pressure [ Nature 2009 , 457 , 863 ]. By using ab initio evolutionary structure search, we report the prediction of ionic boron at a reduced dimension and ambient pressure, namely, the two-dimensional (2D) ionic boron. This 2D boron structure consists of graphene-like plane and B2 atom pairs with the P6/mmm space group and six atoms in the unit cell and has lower energy than the previously reported α-sheet structure and its analogues. Its dynamical and thermal stability are confirmed by the phonon-spectrum and ab initio molecular dynamics simulation. In addition, this phase exhibits double Dirac cones with massless Dirac Fermions due to the significant charge transfer between the graphene-like plane and B2 pair that enhances the energetic stability of the P6/mmm boron. A Fermi velocity (vf) as high as 2.3 × 10(6) m/s, which is even higher than that of graphene (0.82 × 10(6) m/s), is predicted for the P6/mmm boron. The present work is the first report of the 2D ionic boron at atmospheric pressure. The unique electronic structure renders the 2D ionic boron a promising 2D material for applications in nanoelectronics.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology , Gardens Point Campus, Queensland 4001, Brisbane, Australia.
authors.forename: Fengxian
authors.initials: F
authors.lastname: Ma
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology , Gardens Point Campus, Queensland 4001, Brisbane, Australia.
authors.forename: Yalong
authors.initials: Y
authors.lastname: Jiao
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology , Gardens Point Campus, Queensland 4001, Brisbane, Australia.
authors.forename: Guoping
authors.initials: G
authors.lastname: Gao
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology , Gardens Point Campus, Queensland 4001, Brisbane, Australia.
authors.forename: Yuantong
authors.initials: Y
authors.lastname: Gu
authors.affiliation: CSIRO Manufacturing, Virtual Nanoscience Lab , Parkville 3052 Victoria, Australia.
authors.forename: Ante
authors.initials: A
authors.lastname: Bilic
authors.affiliation: Department of Chemistry, University of Puerto Rico , Rio Piedras Campus, San Juan, Puerto Rico 00931.
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology , Gardens Point Campus, Queensland 4001, Brisbane, Australia.
authors.forename: Aijun
authors.initials: A
authors.lastname: Du
keywords: 2D boron; Dirac cones; density functional theory; graphene-like structure; particle swarm optimization