Tendencies in ABO3 Perovskite and SrF2, BaF2 and CaF2 Bulk and Surface F-Center Ab Initio Computations at High Symmetry Cubic Structure

Eglitis, R. I.; Purans, J.; Попов, А. И.; Jia, Ran

doi:10.3390/sym13101920

Cited by 37 publications

(13 citation statements)

References 92 publications

(101 reference statements)

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“…For eigenvalues smearing a 0.02 eV Gaussians of width was chosen. As its well-known that the hybrid exchange-correlation functionals, like B3LYP or B3PW allow to achieve an excellent agreement with the experimental calculations for the band gaps of different materials, [42][43][44][45] whereas the DFTbased methods (eg, GGA, PBE), as a rule underestimate the band gap of those materials [46][47][48][49][50][51] ; Hence, we applied HSE and PBE functionals individually for intrinsic band structure calculations in order to determine band gap oscillation; It was observed that, there is no such bigger fluctuation in band gap values of both functionals for given systems, and a minute variation of $0.04 eV is observed in the energy gaps.…”

Section: Methodsmentioning

confidence: 99%

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Rafique

Osama

Lougou

2022

Intl J of Energy Research

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In this work, density functional theory and molecular dynamics (MD) calculations are performed on TiO x (ie, x = 1-3) doped γ-graphyne to modify its structural, opto-electronic, and spintronic characteristics. Obtained negative binding energies (E b ) values and MD calculations suggest that TiO x substitution in γ-graphyne is thermodynamically stable. Furthermore, the direction of charge transfer occurs from TiO 1(2) clusters to the γ-graphyne, whereas in case of TiO 3 , γ-graphyne lends its charge carriers to impurity cluster. TiO 2(3) cluster doping converts nonmagnetic γ-graphyne to a magnetic material having $2.00 μ B magnetic moment. TiO doped γ-graphyne displays nonmagnetic narrow band indirect semiconductor behavior at M-point with $1.0 eV band gap.Since TiO 2(3) cluster doped γ-graphynes carried magnetic behavior, hence displayed spin polarized band structures. During spin down band, TiO 2 doped γ-graphyne carries $0.7 eV band gap having n-type dopant nature. Similarly, during spin up channel, TiO 3 doped γ-graphyne carries $0.9 eV direct band gap semiconductor behavior. Blue shift appears in absorption and extinction coefficient plots after TiO x substitution in γ-graphyne. Likewise, static reflectivity and refractive index parameters are improved having maximum of 0.65 and 8 peak intensities, respectively. Our obtained results suggest a viable way forward for making functional hybrid γ-graphynes to be used in opto-electronic and spintronic device applications.

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Section: Methodsmentioning

confidence: 99%

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Rafique

Osama

Lougou

2022

Intl J of Energy Research

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“…All calculations are based on the first-principles calculations implemented in the Vienna ab initio Simulation Package (VASP) code [ 17 , 18 ] in the framework of the density functional theory (DFT). To solve the Kohn–Sham equations, the generalized gradient approximation (GGA) within the Perdew–Burke–Ernzerhof (PBE) formulation [ 19 ] or the B3LYP(B3PW) [ 20 , 21 ] is widely used to describe exchange-correlation potential. In this study, we used the former method to describe the exchange-correlation potential.…”

Section: Theoretical Methods and Computational Detailsmentioning

confidence: 99%

Biaxial Tensile Strain-Induced Enhancement of Thermoelectric Efficiency of α-Phase Se2Te and SeTe2 Monolayers

et al. 2021

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Thermoelectric (TE) materials can convert waste heat into electrical energy, which has attracted great interest in recent years. In this paper, the effect of biaxial-tensile strain on the electronic properties, lattice thermal conductivity, and thermoelectric performance of α-phase Se2Te and SeTe2 monolayers are calculated based on density-functional theory and the semiclassical Boltzmann theory. The calculated results show that the tensile strain reduces the bandgap because the bond length between atoms enlarges. Moreover, the tensile strain strengthens the scatting rate while it weakens the group velocity and softens the phonon model, leading to lower lattice thermal conductivity kl. Simultaneously, combined with the weakened kl, the tensile strain can also effectively modulate the electronic transport coefficients, such as the electronic conductivity, Seebeck coefficient, and electronic thermal conductivity, to greatly enhance the ZT value. In particular, the maximum n-type doping ZT under 1% and 3% strain increases up to six and five times higher than the corresponding ZT without strain for the Se2Te and SeTe2 monolayers, respectively. Our calculations indicated that the tensile strain can effectively enhance the thermoelectric efficiency of Se2Te and SeTe2 monolayers and they have great potential as TE materials.

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“…Since the oxygen composition plays a significant role in the phase transition in many material systems, some attempts were executed based on the ab initio calculations to research the formation of oxygen vacancies in the perovskite structure. 9,10 It is worth noting that pronounced MIT and magnetic transitions were usually achieved at x values of ∼2/3 in Re 1−x Sr x FeO 3 with light rare-earth compositions (e.g., La, Pr, and Nd). This was attributed to the charge ordering (CO) in the Fe site following a Fe 3+ -Fe 3+ -Fe 5+ sequence along the <111> axis direction when descending the temperature across a critical point (T CO ) that opens the energy band gap abruptly.…”

Section: ■ Introductionmentioning

confidence: 99%

“…For example, the MIT behaviors were observed in both the high-valence Fe-associated oxides, such as AFeO 3 (A represents alkane earth, e.g., Ca or Ca 1– x Sr x ), Re Cu 3 Fe 4 O 12 ( Re represents rare earth), , and ( Re ,A)FeO 3 , and the low-valence Fe-containing oxides, such as Fe 3 O 4 , Re BaFe 2 O 5 , and Re Fe 2 O 4 . , Taken ( Re ,A)FeO 3 as a representative example, the valence state of Fe can be well controlled by either adjusting the Re /A ratio or the oxygen composition, and this further results in dramatic changes in their crystal and electronic structures as well as electric/magnetic properties. Since the oxygen composition plays a significant role in the phase transition in many material systems, some attempts were executed based on the ab initio calculations to research the formation of oxygen vacancies in the perovskite structure. , It is worth noting that pronounced MIT and magnetic transitions were usually achieved at x values of ∼2/3 in Re 1– x Sr x FeO 3 with light rare-earth compositions (e.g., La, Pr, and Nd). This was attributed to the charge ordering (CO) in the Fe site following a Fe 3+ -Fe 3+ -Fe 5+ sequence along the <111> axis direction when descending the temperature across a critical point ( T CO ) that opens the energy band gap abruptly .…”

Section: Introductionmentioning

confidence: 99%

Rare-Earth Regulation in the Crystal Structure, Electronic Structure, and Metal-To-Insulator Transitions of the High Oxygen Pressure-Annealed Re_0.33Sr_0.67FeO₃

Cui,

Zhang,

et al. 2024

J. Phys. Chem. C

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The complex electromagnetic phase diagram of iron-based perovskites, e.g., Re 0.33 Sr 0.67 FeO 3 (Re stands for rare earth), exhibits a charge/spin ordering transition that enables metal insulator transitions (MIT) beyond conventional oxide semiconductors. While the previous investigations focused on Re 0.33 Sr 0.67 FeO 3 with light or middle rare-earth compositions, Re 0.33 Sr 0.67 FeO 3 containing heavy rare-earth elements beyond Gd have not yet been synthesized owing to their larger intrinsic metastability. Herein, we effectively synthesize Re 0.33 Sr 0.67 FeO 3 covering a large variety of rare-earth elements (e.g., Re = La−Dy) by first forming an oxygen-deficient Re 0.33 Sr 0.67 FeO 3-δ framework via conventional solid-state reactions in air and afterward high-oxygenpressure post annealing that compensates the oxygen composition. Compared to the ones with light or middle rare-earth compositions (e.g., Nd−Eu), the crystal structures of Re 0.33 Sr 0.67 FeO 3 containing heavy rare-earth compositions (e.g., Dy) change from the space group Imma to R3̅ c, while a larger amount of oxygen vacancy is also expected. Consequently, the potentially more distorted FeO 6 octahedron is expected to be balanced by the tendency of generating the oxygen vacancy within Re 0.33 Sr 0.67 FeO 3 containing heavy rare-earth compositions. The heavy rare-earth compositions elevate the Mott temperature T 0 and activation energy E A in their carrier transportations and eliminate their MIT property. Further, on combining with the near-edge X-ray absorption finestructure analysis, an abrupt variation is observed in the Fe-L edge and O-K edge across Re = Sm, and this reflects the boundary of MIT in the material family of Re 0.33 Sr 0.67 FeO 3 when varying the rare-earth compositions. Therefore, pronounced MIT performance is achieved in Re 0.33 Sr 0.67 FeO 3 with light rare-earth compositions and a low oxygen vacancy.

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Tendencies in ABO3 Perovskite and SrF2, BaF2 and CaF2 Bulk and Surface F-Center Ab Initio Computations at High Symmetry Cubic Structure

Cited by 37 publications

References 92 publications

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Biaxial Tensile Strain-Induced Enhancement of Thermoelectric Efficiency of α-Phase Se2Te and SeTe2 Monolayers

Rare-Earth Regulation in the Crystal Structure, Electronic Structure, and Metal-To-Insulator Transitions of the High Oxygen Pressure-Annealed Re_0.33Sr_0.67FeO₃

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Tendencies in ABO3 Perovskite and SrF2, BaF2 and CaF2 Bulk and Surface F-Center Ab Initio Computations at High Symmetry Cubic Structure

Cited by 37 publications

References 92 publications

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO x doped monatomic γ‐graphyne

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO x doped monatomic γ‐graphyne

Biaxial Tensile Strain-Induced Enhancement of Thermoelectric Efficiency of α-Phase Se2Te and SeTe2 Monolayers

Rare-Earth Regulation in the Crystal Structure, Electronic Structure, and Metal-To-Insulator Transitions of the High Oxygen Pressure-Annealed Re0.33Sr0.67FeO3

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Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Density functional theory and ab‐initio molecular dynamics calculations on the opto‐electronic, spintronic, and energies of pure and TiO _x doped monatomic γ‐graphyne

Rare-Earth Regulation in the Crystal Structure, Electronic Structure, and Metal-To-Insulator Transitions of the High Oxygen Pressure-Annealed Re_0.33Sr_0.67FeO₃