Contents lists available at ScienceDirect Materials Science & Engineering B journal homepage: www.elsevier.com/locate/mseb First principle study of mechanical stability, magneto-electronic and thermodynamic properties of double perovskites: A 2 MgWO 6 (A = Ca, Sr) Shabir Ahmad Mir, Saleem Yousuf, Dinesh C. Gupta ⁎ Condensed Matter Theory Group, School of Studies in Physics, Jiwaji University Gwalior, 474011, India ARTICLE INFO Keywords: Density functional theory Double perovskites Elastic constants Cation size and Thermodynamic properties ABSTRACT The first principle method within the framework of density functional theory is employed in order to explore the ground state structure along with electronic, elastic, and thermodynamic properties of double perovskites A 2 MgWO 6 (A = Ca, Sr). Crystal structure optimization reveals nonmagnetic phase as stable state. The computed ground state parameters are consistent with the earlier results. Structural stability is further confirmed through computation of cohesive energy and elastic constants, where we have demonstrated the influence of cation size on various elastic constants. Band profile suggests indirect semiconducting behavior along Γ-X symmetric points for both perovskites. The contribution of different bands is explored through calculation of total and partial density of states. Effects of temperature and pressure on thermodynamic properties are predicted via the quasi- harmonic Debye model to convey the thermodynamic stability of oxides. 1. Introduction ab-initio study within Kohn-Sham (K-S) framework has made it possible to analyze the physical properties of materials from atomic constituent and their spatial configurations using various standard codes [1]. Intensive theoretical and experimental research activities are done over crystalline materials like Heusler alloys [2], chalcogenides [3], skutterudites [4], perovskites [5], etc. possibly due to their pro- mising technological applications. Researchers all over world are looking for smart materials that possess novel properties and are mul- tifunctional. Double perovskite (DP) materials have remained very at- tractive due to their versatile properties ranging from high temperature superconductivity [6], colossal magnetoresistance [7], half metallic (HM) ferromagnetism [8], HM anti-ferromagnetism [9], piezo- electricity and ferroelectricity [10] to multiferrocity [11]. As a result, they have great technological interest with a wide range of possible applications in fields of spintronics, as an electrode material for solid oxide fuel cell, in thermoelectric as an active material for conversion of squander heat into useful energy [12–14]. A lot of research activities are done to explore new DP materials and understand their potential applications in futuristic technologies. DP (A 2 BB′O 6 ) can be derived from simple perovskites (ABO 3 ) by replacing half of B cations with a different B′ cation in 1:1 ratio. The B and B′ cations are ordered in a rock salt manner resulting in idealized Fm-3m cubic structure with lattice constant twice that of ABO 3 perovskite sub cell. With the variations in A, B and B′ cations several structures with different space groups are possible. Empirically, the possible structure of DP can be explored through tolerance factor (t) defined as [15] = + + ′ t r r r r 2( ) A O BB O (1) r A and r O are ionic radii of A cation and oxygen ion, respectively while r BB′ is average of ionic radii of B and B′ cations. If t is in the range of 0.9–1.0, it means that all atoms ideally fit to individual positions re- sulting in ideal cubic structure with Fm-3m space-group. When t = 0.71–0.9, A-cation is small due to which crystal undergo a distor- tion to orthorhombic or rhombohedral structure. However, for t> 1, A-site cations are oversized to fit their positions deforms structure from cubic to hexagonal. From literature survey, we found that investigation on DPs for functional applications dates back to 1961 when ferromagnetic beha- vior of Re-based DPs were reported by Longo and Ward [16]. Since then they have been explored for their properties, however more interest in this field has increased after discovery of half metallicity in Sr 2 FeMoO 6 [7]. Tungsten based DPs have engrossed much attention because of their intriguing and diverse physical properties. Their crystal structure has been crucial; they show variation in crystalline structure and phase transition at higher temperature [17]. Sr 2 BWO 6 (B = Ni, Mg) [18] show the transition from the less symmetric tetragonal phase (I4/m) to the https://doi.org/10.1016/j.mseb.2019.114434 Received 13 November 2018; Received in revised form 16 August 2019; Accepted 11 October 2019 ⁎ Corresponding author. E-mail address: sosfizix@gmail.com (D.C. Gupta). Materials Science & Engineering B 250 (2019) 114434 Available online 25 October 2019 0921-5107/ © 2019 Elsevier B.V. All rights reserved. T