Eur. Phys. J. B (2017) 90: 42
https://doi.org/10.1140/epjb/e2017-70591-0

Regular Article

First principle calculation of accurate native defect levels in CaF₂

¹ Department of Physics, College of Science, Sudan University of Science and Technology, Khartoum 11113, Sudan
² Department of Physics, College of Science, Taibah University, Yanbu, Saudi Arabia
³ Department of Physics, College of Sciences, Al Imam Mohammad Ibn Saud Islamic University (IMSIU), Riyadh 11623, Saudi Arabia

^a e-mail: mkhalfalla@taibahu.edu.sa

Received: 4 October 2016
Received in final form: 1 January 2017
Published online: 8 March 2017

Abstract

We report on the first principle density functional calculation of the charge transition levels of native defects (vacancies and interstitials) in CaF₂ structure. The transition level was defined as the Fermi level where two charge states of given defect have the same formation energy. The common error in the band gap inherited to semiclocal density functional has been accounted for by incorporating the hybrid density functional method, leading to correct placement of the transition levels within the band gap. The band gap size from hybrid calculation has been validated using the full potential, Linearized Augmented Planewave method with the Modified-Becke-Johnson exchange potential. Prior to level calculations, we ensured that an agreement between the formation energies from small (95–97 atoms) and large (323–325 atoms) supercells was achieved after applying the Makov-Payne correction method. Our calculated transition level for the anion vacancy was 2.97 eV below the conduction band, agreeing with the experimental optical absorption band at 3.3 eV associated with the electron transition from the ground state F-center to the conduction band in CaF₂.