First principles calculations of structural, electronic and optical properties of various phases of CaS

Shaukat, A.; Saeed, Yasir; Ikram, N.; Akbarzadeh, Hadi

doi:10.1140/epjb/e2008-00193-x

Cited by 35 publications

(13 citation statements)

References 23 publications

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“…CaS is commonly reported as a wide‐bandgap semiconductor. However, there is considerable variation on the reported bandgap in the literature, with experimental values ranging from 3.4 to 5.8 eV and theoretical predictions from 2.2 to 7.1 eV [ Shaukat et al , ; Waroquiers et al , ; Raubach et al , ]. The bandgap for the CaS powder was determined using the Tauc relation as described in equation [ Tauc et al , ; Tauc , ; Tauc and Menth , ]:

{(h v a)}^{1 true/ n} = A ((), h v - E_{g})

where h is Planck's constant, v is the frequency of vibration, α is the absorption coefficient, E g is the bandgap, and A is a proportionality constant.…”

Section: Resultsmentioning

confidence: 99%

“…CaS is commonly reported as a wide-bandgap semiconductor. However, there is considerable variation on the reported bandgap in the literature, with experimental values ranging from 3.4 to 5.8 eV and theoretical predictions from 2.2 to 7.1 eV [Shaukat et al, 2008;Waroquiers et al, 2013;Raubach et al, 2014]. The bandgap for the CaS powder was determined using the Tauc relation as described in equation (1) [Tauc et al, 1966;Tauc, 1968;Tauc and Menth, 1972]:…”

Section: Discussion Of Mechanism and Determination Of The Cas Bandgapmentioning

confidence: 99%

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Investigating potential sources of Mercury's exospheric Calcium: Photon-stimulated desorption of Calcium Sulfide

Bennett

McLain

Sarantos

et al. 2016

J. Geophys. Res. Planets

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Ground‐based and MErcury Surface, Space ENvironment, GEochemistry, and Ranging observations detected Ca0 and Ca+ in the exosphere of Mercury as well as unexpectedly high levels of sulfur on Mercury's surface. The mineral oldhamite ((Mg,Ca)S) could be a predominant component of the Mercury surface, particularly within the hollows identified within craters, and could therefore serve as a source of the observed exospheric calcium. Laboratory measurements on the photon‐stimulated desorption (PSD) of CaS powder (an analog for oldhamite) at a wavelength of λ = 355 nm have been conducted, utilizing resonance‐enhanced multiphoton ionization time‐of‐flight mass spectrometry to determine the yields and velocity distributions of Ca0. The desorbing Ca0 could be fit using two Maxwell‐Boltzmann components: a 600 (±30) K thermal component and a 1389 (±121) K nonthermal component, the latter accounting for ~25% of the observed signal. Cross sections for PSD using 3.4 eV photons were found to be 1.1 (±0.7) × 10−20 cm2 for Ca0 and 3.2 (±0.9) × 10−24 cm2 for Ca+. Adopting these cross sections, a Monte Carlo model of the release of Ca0 by PSD from the Tyagaraja crater finds the neutral microexosphere created from this process to be substantial even if only 1% CaS is assumed in the hollows. Diffuse reflectance UV‐visible measurements were made on the CaS powder to determine a bandgap, Eg, of 2.81 (±0.14) eV via the Tauc method.

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{(h v a)}^{1 true/ n} = A ((), h v - E_{g})

where h is Planck's constant, v is the frequency of vibration, α is the absorption coefficient, E g is the bandgap, and A is a proportionality constant.…”

Section: Resultsmentioning

confidence: 99%

Section: Discussion Of Mechanism and Determination Of The Cas Bandgapmentioning

confidence: 99%

Investigating potential sources of Mercury's exospheric Calcium: Photon-stimulated desorption of Calcium Sulfide

Bennett

McLain

Sarantos

et al. 2016

J. Geophys. Res. Planets

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“…14,15 At room temperature, CaS crystallizes into a NaCl structure (rock-salt) which is cubic (Fm 3m) with atoms occupying octahedral sites. Calcium cations are arranged in an fcc (face-centered cubic) pattern, and sulfur anions reside in the octahedral holes (see, Fig.…”

Section: -13mentioning

confidence: 99%

Towards controlled synthesis and better understanding of blue shift of the CaS crystals

et al. 2014

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For the first time, the calcium sulfide (CaS) photoluminescent (PL) emission blue shift synthesized by the microwave-assisted solvothermal (MAS) method was examined to understand its key role in the PL activity. PL emission in the visible region showed a blue shift with synthesis time variations. In addition, we also investigated the electronic structure using first-principles calculations based on density functional theory (DFT) which was applied to periodic models at the B3LYP level. Two models were selected to simulate the effects of structural deformation on the electronic structure: (1) the ordered model (o-CaS) and (2) the disordered model (d-CaS). This PL emission shift is linked to distortions and defects which generate modifications in the electronic states and facilitate the possibility of numerous decay transactions to the valence band (VB).

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“…B2-B4 (wurtzite) and B2-B3 (zinc blende) phase transitions have also been predicted (Chen et al, 2007) to occur at low pressure, around 0.829 GPa and 0.679 GPa, respectively. Theoretical calculations based on density functional theory have been successfully employed to calculate the electronic structure, optical properties and thermodynamic parameters (Chen et al, 2007;Shaukat et al, 2008;Guo et al, 2008). The electronic structure varies with the type of exchange-correlation potential functional (Shaukat et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Theoretical calculations based on density functional theory have been successfully employed to calculate the electronic structure, optical properties and thermodynamic parameters (Chen et al, 2007;Shaukat et al, 2008;Guo et al, 2008). The electronic structure varies with the type of exchange-correlation potential functional (Shaukat et al, 2008). Sketch of the cubic crystal structure of calcium sulfide, whose symmetry group is Fm " Furthermore, X-ray absorption spectroscopy is a recognized local structure and element-selective probe to study electronic structures, widely used in different fields.…”

Section: Introductionmentioning

confidence: 99%

Electronic structure and hybridization of CaS by means of X-ray absorption spectroscopy at Ca and S K-edges

Liu

Cui

et al. 2012

J Synchrotron Radiat

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The cubic calcium sulfide (CaS) is a well known system and an attractive building block material for many luminescence technological applications. However, it is essential to achieve an accurate understanding of its electronic structure in order to engineer its band structure for optimized applications. Here a study of the electronic structure of CaS by means of X-ray absorption spectroscopy performed at both Ca and S K-edges, and calculations performed in the framework of the multiple-scattering theory and of the finite difference method are presented. At the Ca K-edge the presence of an anomalous d states feature is discussed while in the S K-edge spectrum the presence of a pre-edge shoulder owing to the hybridization among Ca d states and S p states is pointed out. Although the l-projected density of states of CaS is in good agreement with previous first-principles calculations, the standard muffin-tin potential is inadequate to reproduce near-edge structures at both Ca and S K-edges in this system. Indeed, with its highly symmetric and less compact structure, CaS is characterized by a large set of collinear atomic configurations that pose severe constraints on the construction of the atomic potential. On the contrary, the finite-difference method with no muffin-tin approximation is more suitable for X-ray absorption calculations in this system.

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First principles calculations of structural, electronic and optical properties of various phases of CaS

Cited by 35 publications

References 23 publications

Investigating potential sources of Mercury's exospheric Calcium: Photon-stimulated desorption of Calcium Sulfide

Investigating potential sources of Mercury's exospheric Calcium: Photon-stimulated desorption of Calcium Sulfide

Towards controlled synthesis and better understanding of blue shift of the CaS crystals

Electronic structure and hybridization of CaS by means of X-ray absorption spectroscopy at Ca and S K-edges

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