DFT study of structural, elastic properties and thermodynamic parameters of Bi2S3 under hydrostatic pressuresby Ehsan Zahedi, Bing Xiao

Computational Materials Science

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DFT ies ssib which imply the reliability of the present calculation method. The obtained elastic constants satisfying that the Bi S crystals aremechanically stable up to 9.18 GPa and its hardness is improved under compresemicon mic an orthorhombic structure in the Pnma space group with 4 stoichiometric Bi2S3 units per unit cell. Each molecule contains two bismuth atoms and 3 sulfide atoms which add up to 20 atoms per unit cell [8]. In each unit cell two Bi4S6 ribbons are extended by ionic/covalent bonds along the crystallographic direction [010] (b-axis) [9]. The space between ribbons is depleted of electrons, ical and physical f materials under ts is the ob thor’s know only two high-pressure studies on Bi2S3 can be found in erature. Historically, first pressure effect on Bi2S3 has been s by Lundegaard et al. [25]. They have investigated equation o (EOS) and crystal structure of Bi2S3 at nine distinct hydrostatic pressures in the range 0–9.18 GPa. Furthermore, they showed that the Pnma phase of Bi2S3 is stable up to 9.18 GPa, and lone-electron pairs of Bi moves to the parent atom with increasing in the applied pressure. Next high-pressure study on Bi2S3 has been performed by

Efthimiopoulos et al. [26], applying hydrostatic pressures up to 65 GPa. They studied the high-pressure structural properties and ⇑ Corresponding author. Tel.: +98 9122733755; fax: +98 23 32344634.

E-mail addresses: e_zahedi1357@yahoo.com, e_zahedi@iau-shahrood.ac.ir (E.

Zahedi).

Computational Materials Science 101 (2015) 301–312

Contents lists availab

Computational M lsetoconducting targets, thermoelectric devices, opto-electronic devices, hydrogen storage materials, sensors, and infrared spectroscopy [3–6]. Important member of these semiconductors is

Bi2S3 because of its low toxicity [7]. Bi2S3 has a strongly anisotropic investigations have been reported for the chem properties of Bi2S3. Understanding the behavior o compression based on theoretical or measuremen increasing scientific interest. To the best of the auhttp://dx.doi.org/10.1016/j.commatsci.2015.02.005 0927-0256/ 2015 Elsevier B.V. All rights reserved.ject of ledge, the littudied f statebecause of their novel electronic, magnetic, catalytic, optical and mechanical properties [1,2]. Among 1D semiconductors, nanoribbons have a rectangular cross-section which represent a special geometrical shape [3]. Main group metal chalcogenides AV2B

IV 3 (A = As,Sb,Bi;B = S,Se,Te) are one of the most important nanoribbons and have applications in television cameras with phosolar cells, photodiode arrays, photovoltaic convertors, and photodetectors in visible wavelength region [2,3,5,13,14,19]. Several techniques such as solvothermal process [3,5], hydrothermal technique [20] and low temperature synthesis method [21] have been reported for preparation of Bi2S3 nanoribbons. Several experimental [1,2,4,6,11,12,16,19,22] and theoretical [9,10,23,24]Bi2S3 crystal

Birch–Murnaghan equation of state

Elastic properties

Anisotropy

Thermal conductivity

Thermal expansion coefficient 1. Introduction

Inorganic one-dimensional (1D) s increasing interest in both acade2 3 sion. The surface constructions and planar contours of bulk and Young’s moduli at (100), (010) and (001) crystal planes indicate that bulkmodulus ismore isotropic than Young’smodulus, and anisotropies in both moduli decrease under compression. Furthermore sound velocity, Debye temperature andminimum thermal conductivity are found to be increasing with pressure. The thermal expansion coefficient of Bi2S3 has a strong pressure dependence and its thermal conductivities are extraordinary low which demonstrate its technological application as novel thermal barrier coating materials. Unfortunately, there is currently no experimental measurements of elastic constants and other related properties for comparison.  2015 Elsevier B.V. All rights reserved. ductors have attracted d industrial research and bonding between neighbor ribbons are much weaker than

Bi–S bonds within the ribbons [9,10]. Bi2S3 is a semiconductor [11] with a narrow and direct band gap 1.30–1.70 eV [1–5,9,12– 18], and unique band edge [13] which has been widely used inAccepted 1 February 2015 expansion coefficient of the orthorhombic Bi2S3 in the Pnma structure have been investigated using density functional theory. All calculated properties are in excellent agreement with experimental results,DFT study of structural, elastic propertie parameters of Bi2S3 under hydrostatic pr

Ehsan Zahedi a,⇑, Bing Xiao b aChemistry Department, Shahrood Branch, Islamic Azad University, Shahrood, Iran bDepartment of Earth Sciences, University College London, London WC1E 6BT, United K a r t i c l e i n f o

Article history:

Received 18 November 2014

Received in revised form 29 January 2015 a b s t r a c t

The pressure dependenc anisotropic, linear compre journal homepage: www.end thermodynamic sures om of structural properties, stability, mechanical properties, mechanical ility, Debye temperature, minimum thermal conductivity and thermal le at ScienceDirect aterials Science vier .com/locate /commatsci (1) ateS (1)

Bi 302 E. Zahedi, B. Xiao / Computational MRaman frequencies of layered Bi2S3 with a combination of experimental and theoretical methods. The main outcome of this investigation was the stability of the Pnma phase of layered Bi2S3 up to 50 GPa and appearing of structural disorder at higher pressures. Under pressure, atoms and molecules get closer together, elements become denser, occupied volume decreases and mechanical properties such as bulk modulus and elastic constants can be greatly changed [27]. The knowledge of elastic constants is necessary for many practical applications depending to the mechanical properties of solids such as load deflection, thermoelastic stress, internal strain, sound velocities, fracture toughness, Debye temperature and thermal expansion coefficient [28–30]. Up to now, there are no experimental and theoretical reports on the elastic