title: Mechanical properties of boron-nitride nanotubes after intense femtosecond-laser excitation.
abstract: A femtosecond-laser pulse constitutes an unconventional tool to manipulate solids and nanostructures, for it may excite materials in a transient nonthermal state with hot electrons and atoms close to their initial temperature. Here we study the Young's modulus and the electronic band gap of a (5, 0) zigzag boron-nitride nanotube (BNNT) after an ultrashort laser pulse excitation using density functional theory, where the effect of a femtosecond-laser pulse is modelled by an instantaneous rise of the electronic temperature. At room temperature, before the laser pulse, we obtain a Young's modulus of 763 GPa, which decreases with increasing electronic temperature. For the band gap we find a value of 2.26 eV at room temperature, which increases with increasing electronic temperature and equals 3.28 eV at 28 420 K. We note that conventional means decrease the band gap of BNNTs and that a femtosecond-laser pulse is, to the best of our knowledge, the first tool that increases it. For comparison, we also present results for a (9, 0) zigzag BNNT.
authors.affiliation: Theoretical Physics, University of Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany. Center for Interdisciplinary Nanostructure Science and Technology (CINSaT), Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany.
authors.forename: Bernd
authors.initials: B
authors.lastname: Bauerhenne
authors.forename: Eeuwe S
authors.initials: ES
authors.lastname: Zijlstra
authors.forename: Alan
authors.initials: A
authors.lastname: Kalitsov
authors.forename: Martin E
authors.initials: ME
authors.lastname: Garcia