Predictions on structural, electronic, optical and thermal properties of lithium niobate via first-principle computations

Boukhtouta, M.; Megdoud, Y.; Benlamari, S.; Meradji, H.; Chouahda, Z.; Abdiche, A.; Ghémid, S.; Abu-Jafar, Mohammed S.; Syrotyuk, S. V.; P., D.; Omran, S. Bin; Khenata, R.

doi:10.1080/14786435.2020.1719286

Cited by 13 publications

(5 citation statements)

References 49 publications

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“…This simpler approach, unlike the more complex BSE formalism, allows a direct comparison between one-particle levels (bands) and absorption energies. In this way, we find that the relatively broad defect peak is a superposition of transitions from the single defect level (initial state) into the lowest few conduction bands, namely, Nb 4d states [68,69] centered around 0.2 eV above the conductionband edge. This means that the bipolaron, once excited, is destroyed, and one of the excess electrons is no longer localized at the two involved central Nb atoms but delocalized over several Nb atoms.…”

Section: Modelmentioning

confidence: 83%

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Schmidt

Kozub

Biktagirov

et al. 2020

Phys. Rev. Research

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Polarons in dielectric crystals play a crucial role for applications in integrated electronics and optoelectronics. In this work, we use density-functional theory and Green's function methods to explore the microscopic structure and spectroscopic signatures of electron polarons in lithium niobate (LiNbO 3). Total-energy calculations and the comparison of calculated electron paramagnetic resonance data with available measurements reveal the formation of bound polarons at Nb Li antisite defects with a quasi-Jahn-Teller distorted, tilted configuration. The defect-formation energies further indicate that (bi)polarons may form not only at Nb Li antisites but also at structures where the antisite Nb atom moves into a neighboring empty oxygen octahedron. Based on these structure models, and on the calculated charge-transition levels and potential-energy barriers, we propose two mechanisms for the optical and thermal splitting of bipolarons, which provide a natural explanation for the reported two-path recombination of bipolarons. Optical-response calculations based on the Bethe-Salpeter equation, in combination with available experimental data and new measurements of the optical absorption spectrum, further corroborate the geometries proposed here for free and defect-bound (bi)polarons.

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Section: Modelmentioning

confidence: 83%

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Schmidt

Kozub

Biktagirov

et al. 2020

Phys. Rev. Research

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“…LiNbO3 belongs to a trigonal crystal system and can be describe as hexagonal or rhombohedral primitive unit cell [7] and exhibit in two different phase. At room temperature it possess a ferroelectric phase with a space group of R3c while above its Curie temperature, 1480 K, it exhibit in paraelectric phase with a space group of R3 � c [6,[8][9]. LiNbO3 also possess a high spontaneous polarization of 0.70 C/m 2 at ferroelectric phase [9][10] with a wide band gap energy of 3.78 eV [10].…”

Section: Introductionmentioning

confidence: 99%

Effect of Mn Incorporated into LiNbO<sub>3</sub> Crystal Structure on the Electronic and Optical Properties Using First-Principles Study

Zainuddin

Samat²,

Badrudin

et al. 2023

DDF

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The structural, electronic and optical properties of lithium niobate (LiNbO3) and manganese (Mn)-doped LiNbO3 are investigated using a first-principles study. The first-principles calculation in this work is implemented using CASTEP computer code with GGA-PBE correlation. The band structure and density of states are calculated to analyze the effect of Mn doping on the electronic properties of LiNbO3. Hubbard U correction is applied to Nb 4d state with U= 11 eV and the corrected band gap obtained is 3.771 eV. LiNbO3 doped with Mn shows a reduction in the band gap energy which is 1.9889 eV. The dielectric constant and refractive index of LiNbO3 and Mn-doped LiNbO3 are also calculated. The optical absorption results suggest there is a shift in the absorption edge towards the visible region in comparison with the LiNbO3. The improvement in band gap and optical absorption in Mn-doped LiNbO3 making it a promising material for photovoltaic and photocatalysis applications.

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“…The defect levels involved in the optical excitation must be obtained from a band-structure calculation. The electronic band structure of defect-free stoichiometric LN and the associated density of states are extensively discussed in the literature [41][42][43]51,52] and need not be repeated here. We focus instead on the positions of the one-particle levels inside the fundamental band gap, derived within DFT+U (with U exclusively at the niobium atoms) for the 3 × 3 × 3 supercell containing the defect-bound exciton polaron.…”

Section: Defect Levelsmentioning

confidence: 99%

A Density-Functional Theory Study of Hole and Defect-Bound Exciton Polarons in Lithium Niobate

et al. 2022

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Hole polarons and defect-bound exciton polarons in lithium niobate are investigated by means of density-functional theory, where the localization of the holes is achieved by applying the +U approach to the oxygen 2p orbitals. We find three principal configurations of hole polarons: (i) self-trapped holes localized at displaced regular oxygen atoms and (ii) two other configurations bound to a lithium vacancy either at a threefold coordinated oxygen atom above or at a two-fold coordinated oxygen atom below the defect. The latter is the most stable and is in excellent quantitative agreement with measured g factors from electron paramagnetic resonance. Due to the absence of mid-gap states, none of these hole polarons can explain the broad optical absorption centered between 2.5 and 2.8 eV that is observed in transient absorption spectroscopy, but such states appear if a free electron polaron is trapped at the same lithium vacancy as the bound hole polaron, resulting in an exciton polaron. The dielectric function calculated by solving the Bethe–Salpeter equation indeed yields an optical peak at 2.6 eV in agreement with the two-photon experiments. The coexistence of hole and exciton polarons, which are simultaneously created in optical excitations, thus satisfactorily explains the reported experimental data.

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Predictions on structural, electronic, optical and thermal properties of lithium niobate via first-principle computations

Cited by 13 publications

References 49 publications

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Free and defect-bound (bi)polarons inLiNbO3: Atomic structure and spectroscopic signatures fromab initiocalculations

Effect of Mn Incorporated into LiNbO<sub>3</sub> Crystal Structure on the Electronic and Optical Properties Using First-Principles Study

A Density-Functional Theory Study of Hole and Defect-Bound Exciton Polarons in Lithium Niobate

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