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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.

Electronic-and-optical properties of Rb2ZnCl4 crystals

Andriyevsky B., Kurlyak V., Stadnyk V., Romanyuk M., Stakhura V.

Zeszyty Naukowe Wydziału Elektroniki i Informatyki Politechniki Koszalińskiej

2015

Nr 8

5--14

Electronic-and-optical properties of Rb2ZnCl4 crystal have been studied using the theoretical and experimental methods. First principles calculations of the electronic structure and optical properties using the density functional theory have been performed on the relaxed and uniaxially compressed (1 GPa) Rb2ZnCl4 crystal. The refractive indices of Rb2ZnCl4 have been measured in the spectral range of wavelength 300 nm to 750 nm for three principal uniaxial compression stresses (0.02 GPa) at room temperature. Ab initio calculations and analysis have revealed that the observed uniaxial pressure changes of the refractive indices of Rb2ZnCl4 are caused mainly by the corresponding changes of the crystal unit cell dimensions. The unit cell electronic polarizability of the crystal remains approximately unchanged.

Zbadano właściwości elektronowo-optyczne kryształów Rb2ZnCl4 metodami teoretyczną i doświadczalną. Wykonano obliczenia z pierwszych zasad (ab initio) struktury elektronowej i właściwości optycznych na bazie teorii funkcjonału gęstości zrelaksowanych i jednoosiowo ściśniętych (1 GPa) kryształów. Zostały pomierzone współczynniki załamania Rb2ZnCl4 w przedziale długości fal światła 300 nm do 750 nm dla trzech głównych krystalograficznych kierunków ściskania (0.02 GPa) przy temperaturze pokojowej. Obliczenia ab initio i analiza danych ujawniły, że obserwowane baryczne zmiany współczynników załamania Rb2ZnCl4 są spowodowane głównie odpowiednimi zmianami rozmiarów komórki elementarnej kryształu. Przy tym, polaryzowalność elektronowa komórki kryształu pozostaję się prawie niezmienną.