Prediction of half-metallic properties for the AMnSe 2 (A ¼ Rb, Cs) compounds from first-principle calculations A. Benmakhlouf a,b,n , A. Bentabet c , A. Bouhemadou d,e , A. Benghia b a Département de Physique, Faculté des Sciences Exactes, Université Abderrahmane Mira, Bejaia 06000, Algeria b Laboratoire de Physique des Matériaux, Université Amar Telidji, BP 37G, Laghouat 03000, Algeria c Laboratoire de Recherche: Caractérisation et Valorisation des Ressources Naturelles, Université de Bordj Bou Arreridj, 34000, Algeria d Laboratory for Developing New Materials and their Characterization, University of Setif 1, Setif 19000, Algeria e Department of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia article info Article history: Received 18 July 2015 Received in revised form 22 September 2015 Accepted 24 September 2015 Available online 28 September 2015 Keywords: First-principle calculations GGA and GGAþU Spin-polarized Half-metallic Ternary chalcogenides Elastic constants abstract Using first-principle calculations method based on spin-polarized density functional theory, we have predicted the half-metallic character of the AMnSe 2 (A ¼Rb, Cs) layered compounds. The structural, electronic, magnetic and elastic properties of these ternary chalcogenides crystals have been in- vestigated. The electronic exchange-correlation energy has been described by the generalized gradient approximation GGA and the GGA þU (U is the Hubbard correction). Our calculated structural parameters are in good agreement with the available experimental data. The calculated total magnetic moment is equal to 4.00 B μ for both studied compounds. Architecture of the electronic states near the Fermi level has been explored and the origin of the gap in the considered half-metallic alloys has been determined. Single-crystals and polycrystals elastic moduli and related properties for both investigated materials have been examined. & 2015 Elsevier B.V. All rights reserved. 1. Introduction Initially predicted by de Groot and collaborators [1] and ver- ified by other authors [2–6], the half-metallic ferromagnets (HMF) alloys are amongst the most promising materials for possible ap- plication in magnetism and spin electronic devices [7–9]. At the Fermi level E F of the HMF, the majority-spin band is of metallic character and the minority-spin band is semiconducting, resulting in 100% spin polarization, which maximizes the efficiency of spintronic devices [7,10]. As described by de Groot and M Mueller [1], the half metallic behavior in a material is closely related to the crystal structure, valence-electron count, covalent bonding and large splitting of the d-electron band states. Many material classes are half-metallic. Besides half- and full- Heusler alloys, there are other families of materials which are half- metallic systems, e.g., some metallic oxides like CrO 2 and Fe 3 O 4 , zinc-blende compounds like CrAs and CrSb and some manganite like La 0.7 Sr 0.3 MnO 3 [11–18]. An intensive scientific effort has been devoted to the investigation of the ternary manganese chalco- genides A–Mn–Q, where A ¼ alkali metal and Q ¼ chalcogenides [19–25]. In 1999, Kim and Hughbanks [26] reported the synthesis, structural characterization and magnetic properties of the ternary metal chalcogenides RbMnSe 2 and CsMnSe 2 . To the best of our knowledge, this is the only study that was devoted to these two compounds. The understanding of the electronic and magnetic properties of RbMnSe 2 and CsMnSe 2 may give an insight related to their performance in the field of magnetic and spintronic appli- cations. Therefore, a detailed study of the title compounds is ne- cessary to get a more complete picture of their physical properties. In this work, we aim to provide a detailed study of the struc- tural, elastic, electronic and magnetic properties of the RbMnSe 2 and CsMnSe 2 compounds. The present study was carried out by using first-principle plane-wave pseudo-potential total energy calculations. This paper is organized as follows. We briefly de- scribe the used calculational methods in Section 2. The obtained results are reported and discussed in Section 3. The most im- portant conclusions and remarks drawn from our present theo- retical study are given in Section 4. 2. Method of calculations All present calculations were carried out using pseudo-poten- tial total energy method with plane-wave basis as implemented in the CASTEP Package [27]. The tightly bound core electrons were Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jmmm Journal of Magnetism and Magnetic Materials http://dx.doi.org/10.1016/j.jmmm.2015.09.078 0304-8853/& 2015 Elsevier B.V. All rights reserved. n Corresponding author at: Département de Physique, Faculté des Sciences Exactes, Université Abderrahmane Mira, Bejaia 06000, Algeria. E-mail address: a.benmakhlouf@lagh-univ.dz (A. Benmakhlouf). Journal of Magnetism and Magnetic Materials 399 (2016) 179–184