Eur. Phys. J. B (2016) 89: 198
https://doi.org/10.1140/epjb/e2016-70341-x

Regular Article

Optical absorption spectra of boron clusters B_n (n = 2–5) for application in nano scintillator – a time dependent density functional theory study

¹ Radiation Safety System Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India
² High Pressure & Synchroton Radiation Physics Division, Bhabha Atomic Research Centre, Trombay, Mumbai, India

^a e-mail: rkshivade@barc.gov.in

Received: 27 May 2016
Received in final form: 21 June 2016
Published online: 14 September 2016

Abstract

Boron nano-clusters of various shapes and sizes have potential applications as scintillating detector and hydrogen storage material. Using time dependent density functional theory (TDDFT) as implemented in CASIDA we have studied the linear optical absorption spectra for boron clusters B_n (n = 2–5) and compared with previously reported results using Hatree-Fock (H-F) based method where the spectrum is limited to 8 eV due to exclusion of excitation into very high energy unoccupied orbital. The optical spectra fall in the visible and near UV region and are very much dependent on the shape of the isomer. We have obtained additional peaks for B₂ linear, B₃ triangular, B₄ rhombus and square shaped isomers beyond 8 eV which were missing in the previous H-F based study and has significance as they fall below the ionization potential. We correlate the optical spectrum with the shape of the Kohn-Sham orbitals and HUMO-LUMO gap and assess comparative stability of various B_n (n = 2–5) clusters in terms of HUMO-LUMO gap, bond-length and relative energy. TDDFT computed optical spectroscopy correlated with Kohn-Sham orbitals and HUMO-LUMO gap and its comparison with H-F based method may give significant knowledge regarding geometry and optical properties of B_n (n = 2–5) clusters enabling to distingush between various isomers of B_n clusters.