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First principles investigations of HgX (X=S, Se and Te)

Düz I., Erdem I., Ozdemir Kart S., Kuzucu V.

Archives of Materials Science and Engineering

2016

Vol. 79, nr 1

5--11

Purpose: The aim of this study is to determine the structural, and mechanical properties of Hg chalcogenide materials (HgX; X=S, Se, Te) in the zinc-blende structure which are presented as promising candidates for modern optoelectronic and spintronic applications. The dependence of elastic constants of pressure for three materials are evaluated. Moreover, isotropic mechanical properties such as bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio are obtained. Design/methodology/approach: First principles calculations based on Density Functional Theory are performed by employing Projector Augmented Waves potentials. The electronic exchange and correlation function is treated by using Generalized Gradient Approximation parametrized by Perdew, Burke and Ernzerhof (PBE96). Findings: Calculated results of structural and mechanical properties are in good agreement with those of experimental and other theoretical studies. This three materials in zinc-blende structure are mechanically stable. İsotropic mechanical properties are also obtained. Resistance against both linear strain and shear strain and ductility decrease as we go into the sequence of HgS−>HgSe−>HgTe. The wave velocities and Debye temperatures calculated for this materials. Debye temperatures are founded for HgS, HgSe and HgTe as 306.21 K, 264.30 K and 240.19 K, respectively Research limitations/implications: Calculation speeds of the computers and data storage are some limitations. Also, the lack of experimental data hinder for the comparison of our results. Practical implications: Obtaining high pressure elastic constants by calculations is preferable since it is very difficult or even impossible to measure them by experimentally. Originality/value: There are only restricted number of investigation of elastic constants of mercury chalcogenides both theoretically and experimentally.

First principles studies of SnO at different structures

Erdem I., Hüseyin Kart H., Cagin T.

Archives of Materials Science and Engineering

2010

Vol. 45, nr 2

108-113

Purpose: Structural and mechanical properties of the Sn (tin) based oxides SnO and SnO2 are investigated. The aim of this study to determine in which structural phase SnO is found and to calculate its elastic constants at different pressures. Design/methodology/approach: Calculations have been made for three different structures of SnO by density functional theory (DFT). The behavior of structural parameters (lattice constants, internal parameters) and bulk modulus under different pressures, and elastic constants are calculated by using ab initio calculations. Generalized Gradient Approximation (GGA) and Perdew-Burke-Ernzerhof (PBE) parameterization is used. Findings: All of six elastic constants of litharge SnO and three elastic constants of rocksalt structure of SnO are calculated for the first time in this study. Among three structures of SnO, namely, rocksalt, cesium chloride and tetragonal litharge, the most energetically favorable one is the litharge structure at ambient conditions. The calculation of enthalpies with respect to pressure shows that any phase transition from litharge to rocksalt structure does not occur by applying the pressures of up to 5 GPa to the systems. Equilibrium volume, energy and bulk modulus of rutile SnO2 are also calculated. Our results are compared with other available experimental data and theoretical results. Research limitations/implications: Computer calculation speeds and its information storage area are limitations, it will be possible to reach experimental results as near as in condition that they are improved. Practical implications: It is very difficult to measure elastic constants especially under high pressure experimentally. However, they are calculated by first principles calculations. Originality/value: Behavior of elastic constants and structural parameters under high pressures are determined for the first time in this study. Simulations can lead experimentalist to find new applications of these technologically important materials.