Chemical Physics Letters 635 (2015) 228–233 Contents lists available at ScienceDirect Chemical Physics Letters jou rn al h om epa ge: www.elsevier.com/locate/cplett Shine blue and blue-green photoluminescence in BaZrO 3-ı powders: An Ab-initio analysis of structural deformation Kh. Dhahri a , M. Bejar a,∗ , E. Dhahri a , M.F.P. Grac ¸ a b , A. Zaoui c a Laboratoire de Physique Appliquée, Faculté des Sciences, Université de Sfax, B.P. 1171, 3000 Sfax, Tunisia b I3N and Physics Department, University of Aveiro, 3810-193 Aveiro, Portugal c Laboratoire de Physique Computationnelle des Matériaux – LPCM, Université Djillali Liabes de Sidi Bel-Abbes, 22000 Sidi Bel-Abbes, Algerie a r t i c l e i n f o Article history: Received 21 February 2015 In final form 21 June 2015 Available online 7 July 2015 a b s t r a c t A blue and blue-green photoluminescent emission for BaZrO 3-ı powders was measured. A Plane Wave Self-Consistent Field method, based on the density functional theory and the local density approximation, was carried out to rationalize this phenomenon. The theoretical results showed that local defects in the cubic structure, caused by oxygen vacancies, play an important role in the formation of new level energy into the band gap, giving rise to the PL emission. DOS calculation showed that the new levels were linked to the d-orbital of both Ba and Zr atoms. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Recently, much attention has been given to the photolumi- nescence (PL) properties of titanates and zirconates with an ordered–disordered perovskite structure. This is thanks to their excellent optical and electrical properties at room temperature. For example, an intense violet-blue and green photoluminescence was observed in BaZrO 3 by Cavalcante et al. [1,2]. Dhahri et al. and D. Kan et al. have investigated the effect of the oxygen vacancy on the pho- toluminescence propriety. They have found an intense blue-green [3], red-yellow [4] and blue [5] photoluminescence in BaZrO 3-ı , GdAlO 3-ı and SrTiO 3-ı powders, respectively. Orhan et al. [6] and Pontes et al. [7] have studied the role of network modifiers in the creation of photoluminescence in BaTiO 3 and CaTiO 3 compounds. The photoluminescence properties of the perovskite with ordered–disordered structure were found to be related to the fact that intrinsic defects occur within this structure, leading to the appearance of electronic states inside the band gap [7]. These defects can be linked to three types of mechanisms V O z = V O x , V O • and V O •• , where the singly ionized mechanism V O • captures one electron ↑ , doubly ionized mechanism V O •• is not able to trap electrons and neutral mechanism V O x captures up to two paired electrons ↑↓ [3]. In the literature, several theoretical and experimental works have studied the effect of the singly ionized oxygen vacancy ∗ Corresponding author. E-mail address: zmordaessebti99@yahoo.fr (M. Bejar). mechanism V O • on the PL properties of perovskite titanates and zirconates, such as BaTiO 3 , SrTiO 3 , CaTiO 3 and BaZrO 3 [8–11]. Cav- alcante et al. [2] and Gurgel et al. [12] investigated the effect of the atomic displacements in the BaZrO 3 compound and proposed a theoretical model based on DFT method. Using the densities of states (DOS) calculations, Cavalcante et al. found that the displace- ments of Zr atoms favored an asymmetry in the system, allowing the appearance of new states inside the band gap region where an electron and a hole can recombine, giving rise to the PL emission. Those new states were identified as the 2p orbital of the singly ionized oxygen atoms. However, to our knowledge, there are no proposed theoretical works, which studied the effect of the zed oxygen vacancy on the PL properties of perovskites. The aim of this work is to present a theoretical study investigat- ing the effect of the oxygen vacancy on the electronic structure to explain the origin of the blue-green PL emission observed for the BaZrO 3-ı (BZO) compounds. 2. Computational details and methods The theoretical calculations were performed using an integrated suite of computer codes for electronic structure and materials modeling based on the density functional theory (DFT) method, plane waves and ultra-soft pseudo-potentials. The self-consistent calculations were carried out with a scalar-relativistic version of the Plane Wave Self-Consistent Field (PWSCF) embodied in the QUANTUM-ESPRESSO package [13]. The exchange-correlation was treated in the framework of the local density approximation (LDA) with the parameterization of Perdew and Zunger (PZ) [14]. The http://dx.doi.org/10.1016/j.cplett.2015.06.069 0009-2614/© 2015 Elsevier B.V. All rights reserved.