Structural, electronic, vibrational, mechanical and thermoelectric properties of 2D and bulk BaX (X=O, S, Se and Te) series under DFT and BTE framework

Kumar, Pankaj; Rajput, Kaptan; Roy, Debesh R.

doi:10.1016/j.physe.2020.114523

Cited by 20 publications

(16 citation statements)

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“…Typically, the sulfides exhibit wider band gaps than the respective selenides, and the calcium chalcogenides show wider band gaps than their strontium and barium counterparts (Figure , Table ). ,− Some of the selenides absorb slightly in the visible range. For instance, ∼15 nm BaSe exhibits a band gap of 2.69 eV (461 nm), and both bulk and nanosized BaSe also exhibit a small secondary absorption edge in the visible region (see the Supporting Information).…”

Section: Resultssupporting

confidence: 91%

“…We first established a control calculation using the better-known electronic properties of rock salt BaSe. Both the band structure and DOS reveal an indirect band gap of 2.20 eV at the Γ and X high-symmetry points (see the Supporting Information), in close agreement with other computational studies. − This method underestimates the experimental band gap by 35%, which is consistent with the amount of variance typically observed using LMTO-ASA. , …”

Section: Resultssupporting

confidence: 87%

“…Specifically, the edge Se 4p orbitals contribute to both the VBM and CBM, whereas the center Se 4p orbitals contribute mainly to the CBM. Overall, our computational results agree well with absorbance measurements, and supports the trend in band gap: BaSe > BaSe 2 > BaSe 3 . , …”

Section: Resultssupporting

confidence: 85%

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Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability

et al. 2022

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Increasing demand for effective energy conversion materials and devices has renewed interest in semiconductors comprised of earth-abundant and biocompatible elements. Alkaline-earth sulfides doped with rare earth ions are versatile optical materials. However, relatively little is known about controlling the dimensionality, surface chemistry, and inherent optical properties of the undoped versions of alkaline-earth mono- and polychalcogenides. We describe the colloidal synthesis of alkaline-earth chalcogenide nanocrystals through the reaction of metal carboxylates with carbon disulfide or selenourea. Systematic exploration of the synthetic phase space allows us to tune particle sizes over a wide range using a mixture of commercially available carboxylate precursors. Solid-state NMR spectroscopy confirms the phase purity of the selenide compositions. Surface characterization reveals that bridging carboxylates and amines preferentially terminate the surface of the nanocrystals. While these materials are colloidally stable in the mother solution, the selenides are susceptible to oxidation over time, eventually degrading to selenium metal through polyselenide intermediates. As part of these investigations, we have developed the colloidal syntheses of barium di- and triselenides, two among few reported nanocrystalline alkaline-earth polychalcogenides. Electronic structure calculations reveal that both materials are indirect band gap semiconductors. The colloidal chemistry presented here may enable the synthesis of more complex, multinary chalcogenide materials containing alkaline-earth elements.

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Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 87%

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Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability

et al. 2022

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“…[16][17][18][19][25][26][27][28][29] Therefore, understanding the high pressure structural and lattice dynamical behavior of BaO is crucial as this can be a possible candidate of the Earth's mantle. 12 Several high pressure X-ray diffraction (HP-XRD) measurements 23,[29][30][31][32][33][34][35] and theoretical studies using first principles calculations were focused on exploring the structural phase transitions, 18,21,25,27,[36][37][38][39] metallization, 20,[40][41][42][43][44][45][46] elastic properties, [47][48][49][50] thermodynamic stability 25,51,52 of MO (M = Mg, Ca, Sr, Ba) compounds under high pressure. Similarly, efforts have been put forward by the researchers to explore the phase diagram of BaO under high pressure from both experimental and theoretical perspective.…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, lattice dynamics of B1 phase is well studied at ambient as well as at high pressure using first principles calculations 16,51,56,57 and inelastic neutron scattering technique. 58 However, very limited studies 52 are available exploring lattice dynamics of high pressure phases, underlying mechanisms behind the observed structural phase transitions and spectroscopic properties under high pressure in BaO.…”

Section: Introductionmentioning

confidence: 99%

Lattice instability and Raman spectra of BaO under high pressure: A first principles study

Lavanya,

Yedukondalu,

Roshan

et al. 2022

Preprint

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Alkaline-earth metal oxides, in particular MgO and CaO dominate Earth's lower mantle, therefore, exploring high pressure behavior of this class of compounds is of significant geophysical research interest. Among all these compounds, BaO exhibits rich polymorphism in the pressure range of 0-1.5 Mbar. Static enthalpy calculations revealed that BaO undergoes a pressure induced structural phase transition from NaCltype (B1) → NiAs-type (B8) → distorted CsCl-type (d-B2) → CsCl-type (B2) at 5.1, 19.5, 120 GPa respectively. B1 → B8 & B8 → d-B2 transitions are found to be first order in nature whereas d-B2→ B2 is a second order or weak first order phase transition. Interestingly, d-B2 phase shows stability over a wide pressure range, ∼19.5-113 GPa. Mechanical and dynamical stabilities of ambient and high pressure phases are demonstrated through computed elastic constants and phonon dispersion curves, respectively. Under high pressure, significant phonon softening and soft phonon mode along M-direction are observed for B8, d-B2 and B2 phases, respectively. Pressure dependent Raman spectra suggest a phase transition from d-B2 to Raman inactive phase under pressure. Overall, the present study provides a comprehensive understanding of underlying mechanisms behind pressure-induced structural phase transitions in BaO.

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Thionation‐Induced Enhancement of Optical and Electronic Properties in NDI Molecule for Molecular Electronic Applications: A Computational Study Using DFT/TD‐DFT and QTAIM Theory

Hadi,

Shamlouei

2024

Advcd Theory and Sims

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The study investigates the impact of thionation on N,N'‐di(dodecyl)‐4,5,8,9‐naphthalene diimide (NDI) through computational methods such as density functional theory (DFT/TD‐DFT), quantum theory of atoms in molecules (QTAIM), and Landauer theory (LT). Thionation, involving the replacement of diamide oxygens with sulfurs in NDI, significantly enhances quantum‐electronic/thermoelectric properties. Computational analyzes of energy of frontier orbitals HOMO/LUMO, dipole moment, polarizability, first superpolarizability, UV spectrum, and cohesive energy show the superior performance of the thione structure (M2) compared to the pristine structure (M1). Thionation decreased the energy gap from 01.3 eV (in M1 structure) to 1.87 eV (in M2 structure). The absorption wavelength in the pristine structure (M1) is calculated to be 507 nm, which increased to 1067 nm after thionation (M2). Cohesive energy values for each of M1 and M2 structures are calculated as 12.76 and 12.89 Kcal mol−1, respectively, which indicates the improvement of stability after thionation. After connecting M1 and M2 to gold electrodes (Au‐M1‐Au and Au‐M2‐Au) and applying electric fields, the Au‐M2‐Au structure shows a lower energy gap, lower thermoelectric activity and higher conductivity at field intensities with higher than 140 × 10−4 (a.u.), indicating its use as a field‐effect molecular device (such as molecular wire or molecular switch).

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Structural, electronic, vibrational, mechanical and thermoelectric properties of 2D and bulk BaX (X=O, S, Se and Te) series under DFT and BTE framework

Cited by 20 publications

References 50 publications

Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability

Alkaline-Earth Chalcogenide Nanocrystals: Solution-Phase Synthesis, Surface Chemistry, and Stability

Lattice instability and Raman spectra of BaO under high pressure: A first principles study

Thionation‐Induced Enhancement of Optical and Electronic Properties in NDI Molecule for Molecular Electronic Applications: A Computational Study Using DFT/TD‐DFT and QTAIM Theory

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