Computational Materials Science

(1)

Structural, elastic, electronic, chemical bonding and optical properties of Cu-based oxides ACuO (A = Li, Na, K and Rb): An ab initio study

A. Bouhemadou

^a,^⇑

, O. Boudrifa

^a

, N. Guechi

^a

, R. Khenata

^b

, Y. Al-Douri

^c

, S ß . Ug˘ur

^d

, B. Ghebouli

^e

, S. Bin-Omran

^f

aLaboratory for Developing New Materials and their Characterization, Department of Physics, Faculty of Science, University of Setif 1, 19000 Setif, Algeria

bLaboratoire de Physique Quantique et de Modélisation Mathématique (LPQ3M), Département de Technologie, Université de Mascara, 29000 Mascara, Algeria

cInstitute of Nano Electronic Engineering, Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia

dGazi University, Faculty of Science, Department of Physics, Teknikokullar, Ankara 06500, Turkey

eDepartment of Physics, University of Setif 1, 19000 Setif, Algeria

fDepartment of Physics and Astronomy, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia

a r t i c l e i n f o

Article history:

Received 7 May 2013

Received in revised form 4 September 2013 Accepted 5 September 2013

Available online 30 September 2013

Keywords:

Cu-based oxides Ab initiocalculations Elastic constants Electronic properties Chemical bonding Pressure effect

a b s t r a c t

Ab initiototal energy calculations were performed to study in details the structural, elastic, electronic, chemical bonding and optical properties of Cu-based ternary oxides ACuO (A = Li, Na, K and Rb).

Optimized atomic coordinates and lattice constants agree well with the existing experimental and theoretical data. Numerical estimations of the six independent elastic constantsCijand their related properties for monocrystalline ACuO were obtained. A set of elastic moduli for polycrystalline ACuO, namely bulk modulusB, shear modulusG, Young’s modulusE, Poisson’s ratior, Lamé coefﬁcientskand Debye temperaturehDwere evaluated. Band structure, total and site-projectedl-decomposed densities of states, charge-carrier effective masses, charge transfers and charge density distribution maps were obtained;

analyzed and compared with the available theoretical data. Complex dielectric function, refractive index, extinction coefﬁcient, reﬂectivity and loss function spectra were calculated with an incident radiation polarized parallel to both [1 0 0] and [0 0 1] crystalline directions.

1. Introduction

Noncentrosymmetric (NCS) oxide materials are the basis for numerous applications due to their symmetry dependent properties such as pyroelectricity, piezoelectricity, ferroelectricity and second-order non linear optical (NLO) behavior[1; and references therein]. ACuO compounds, where A = Li, Na, K and Rb, belong to the NCS non-polar crystals. At ambient conditions ACuO compounds crystallize in the tetragonal KAgO-type structure[1–4].

Theoretical and experimental information on the ACuO compounds, where A is an alkaline metal (Li, Na, K and Rb), are rather scarce. On the experimental side, Klassen and Hope[2], Losert and Hope[3]and Fischer et al.[4]have reported some information on the elaboration and structural properties of these compounds. The X-ray diffraction analysis of elaborated single crystals [2–4] revealed the tetragonal crystalline structure of the ACuO materials.

Theoretically, Umamaheswari and co-workers[1] have reported some results on the structural and electronic properties of the ACuO crystals using the tight-binding linear mufﬁn-tin orbital (TB-LMTO) method within the local density approximation (LDA).

From the energy–volume relations, they found that these materials are stable in the tetragonal KAgO-type structure (symmetry group I4/mmm) at ambient conditions and undergo structural phase transition to hypothetical cubic structure in the high pressure region. The results of their electronic band structure calculations revealed the semiconducting nature of these materials. To the best of the authors’ knowledge, some fundamental physical properties of the ACuO materials, such as the elastic constants and their related properties, chemical bonding, charge-carrier effective mass and optical properties, are still lacking.

It is well known that knowledge of the elastic properties of materials is important because of their closely relations with vari- ous fundamental physical properties. In particular, they provide information on the stability and stiffness of the materials against externally applied stresses. Knowledge of the pressure dependence of elastic constants and lattice parameters are the most significant in many modern technologies[5]. For example, semiconductor lay- ers are commonly subjected to a large built-in strain since they are often grown on different substrates having considerable lattice mismatch[6,7]. Measurements of elastic moduli and lattice constants under pressure are generally very difficult, so the lack of experimental data can be compensated by theoretical simulation based on accurate ab initio theories. Thus, the first objective of

http://dx.doi.org/10.1016/j.commatsci.2013.09.011

⇑ Corresponding author. Tel./fax: +213 36620136.

E-mail address:a_bouhemadou@yahoo.fr(A. Bouhemadou).

Computational Materials Science 81 (2014) 561–574

Contents lists available atScienceDirect

Computational Materials Science

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o m m a t s c i