Optik 124 (2013) 2670–2673 Contents lists available at SciVerse ScienceDirect Optik j o ur nal hom epage: www.elsevier.de/ijleo Energy levels and deformation potentials for rocksalt MgO A. Gueddim a , N. Bouarissa b,c,∗ , A. Villesuzanne d a Department of Electronics, University of Djelfa, 17000 Djelfa, Algeria b Department of Physics, College of Science and Arts, Najran University, Najran, P.O. Box 1988, Saudi Arabia c Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, Najran 11001, Saudi Arabia d ICMCB-CNRS, University of Bordeaux 1, 87 Av. Dr. A. Schweitzer, 33608 Pessac Cedex, France a r t i c l e i n f o Article history: Received 20 April 2012 Accepted 1 August 2012 PACS: 71.15.Nc 71.20.-b 71.20.Be 71.20.Nr Keywords: Electronic properties High-pressure MgO Ab initio calculations a b s t r a c t We have studied the high-pressure behavior of the electronic properties of periclase (MgO) using ab initio total energy calculations within the full-potential linearized augmented plane wave method in the framework of the density functional theory. We predict that at zero pressure MgO in the rocksalt structure is a semiconductor with a direct band gap of 5.35 eV We show that the material remains a direct band gap semiconductor under pressures up to 100 GPa. We report the pressure coefficients and deformation potentials of the three transitions  – ,  –X and  –L for the material in question. We also find that the valence band width increases monotonically with increasing pressure suggesting that the rocksalt MgO becomes less ionic under pressure. © 2012 Elsevier GmbH. All rights reserved. 1. Introduction The electronic properties of minerals at high pressure are of substantial physical interest. Periclase (MgO) is one of the major earth-forming minerals. It is easily made by burning magnesium ribbon which oxidizes in a bright white light, resulting in a pow- der. In nature it is hygroscopic and care must be taken to protect it from moisture. Only one solid phase, with the NaCl-type structure, has been observed for temperature up to the melting and pressures up to 227 GPa [1]. Thus, periclase has traditionally been regarded as a standard solid for calibrating pressure in experiments at extreme conditions [2]. The study of materials at high pressures is experiencing great current activity. High pressure can have a very large effect on the chemical and physical properties of matter and materials often exhibit novel behavior under pressure. As a matter of fact, pressure changes the lattice constant of the material of interest and, hence, produces shifts of the electronic states in the crystal. It can also change the band extrema from one point of the Brillouin zone to another one leading, thus to new electronic properties of the crys- tal under load [3–7]. Pressed MgO is used as an optical material. ∗ Corresponding author at: Department of Physics, College of Science and Arts, Najran University, Najran, P.O. Box 1988, Saudi Arabia. E-mail address: N Bouarissa@yahoo.fr (N. Bouarissa). Experimental investigations of MgO are now possible over consid- erable ranges of pressure and temperature [2,8–10]. In addition to the experimental advances, reliable computational methods for electronic band structure and total energy calculation have made a substantial impact on high-pressure behavior of MgO [11–16]. In the present paper, the electronic properties of rocksalt MgO at zero and under pressure are reported. The aim of this work is to examine the electronic band structure of MgO in the rocksalt structure, with emphasis on its dependence on high pressure. The calculations are performed using ab initio full-potential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) [17] where the exchange and correlation effects were treated using the Engel and Vosko generalized gra- dient approximation (EV-GGA) [18]. Features, such as electronic band structure, direct and indirect energy band-gaps and valence band width (VBW) and their pressure dependence for rocksalt MgO are presented and discussed. The pressure dependence of these features has allowed the determination of band gap deformation potentials and linear pressure coefficients of the three transitions considered here. 2. Computational methodology The calculations performed here were based on DFT [17] using the FP-LAPW method as implemented in the WIEN2K code [19]. In dealing with electron–electron interaction, the exchange 0030-4026/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2012.08.092