Structural transition and mechanical properties of one dimensional boron ribbons and chains from first principles

The past decade has brought great progress in fabrication and characterization of single-atom chains of carbon (carbyne). Very recently novel atomic chain compositions such as BN and CsI were reported. The extreme and unusual properties of such 1D materials\footnote{M. Liu \emph{et al.}, \emph{ACS Nano} 7, 10075 (2013)}\footnote{V. I. Artyukhov, M. Liu, and B. I. Yakobson, \emph{Nano Lett.} 14, 4224 (2014)} motivate the search for other possible compositions with interesting behaviors. We use first-principles calculations to uncover the rich structural and mechanical properties of 1D boron. While the ground state structure of linear boron is a two-atoms-wide ribbon, tension can unravel it into a single-atom string structure. We analyze the mechanical and electronic properties of these two ``phases'' and study the thermodynamics and kinetics of transition between them using static first-principles calculations and semiempirical (DFTB) molecular dynamics. The interesting properties of 1D boron nanostructures make them an attractive system for experimental investigations.