Raman scattering by longitudinal and transverse optical vibrations in lithium niobate single crystals

Горелик, В. С.; Sverbil, P. P.

doi:10.1134/s0020168515100076

Cited by 33 publications

(19 citation statements)

References 4 publications

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“…Pseudoscalar modes of A 2 type are forbidden for a perfect LN crystal IR and Raman spectra, but they are allowed in the hyper-Raman spectrum ( Table 1). According to the data of group-theoretical analysis for a perfect LN crystal, the phonon dispersion curve has 30 oscillatory branches; 27 of them are optical and 3 are acoustic [5,36,[55][56][57][58]. Since there is no alternative prohibition, due to absence of an inversion center, Raman active optical vibrations must also manifest themselves in IR absorption spectra.…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

“…Since there is no alternative prohibition, due to absence of an inversion center, Raman active optical vibrations must also manifest themselves in IR absorption spectra. 4A 1 + 9E dipole active fundamental oscillations are active in Raman scattering and IR absorption at k = 0 (in the center of the Brillouin zone) [5,36,[55][56][57][58]. All optical vibrations (except A 2 ) have a polar nature, thus they are split in the crystal into longitudinal (LO) and transverse (TO).…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

“…A 2 oscillations related to the pseudoscalar type of symmetry are forbidden in the vibrational spectrum of a perfect LN crystal at k = 0. They are also not dipole-active and do not experience LO-TO splitting [5,55,56]. However, A 2 symmetry type oscillations are allowed for the processes of hyper-Raman scattering [56].…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

“…They are also not dipole-active and do not experience LO-TO splitting [5,55,56]. However, A 2 symmetry type oscillations are allowed for the processes of hyper-Raman scattering [56].…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

“…The Raman spectrum of polaritons depends on the angle of collection of scattered radiation [5,55]. As numerous studies show, significantly more bands are observed in the Raman spectra of real crystals than allowed by the selection rules for a structure characterized by the spatial symmetry group C 3V 6 (R3c) with two formula units per the unit cell [5,11,[36][37][38][39][40][41][42]55,56,[59][60][61][62][63][64][65][66][67]. In addition to the bands corresponding to the fundamental lattice vibrations, a number of low-intensity bands are observed in the spectrum-the so-called extra bands.…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

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Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

2019

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Raman spectra of lithium niobate single crystals strongly doped by zinc and magnesium, it has been established, contain low-intense bands with frequencies 209, 230, 298, 694, and 880 cm −1 . Ab ignition calculations fail to attribute these bands to fundamental vibrations of A 2 symmetry type unambiguously. Such vibrations are prohibited by the selection rules in the space group C 3V 6 (R3c).Ab initio calculations also proved that low-intense "extra" bands with frequencies 104 and 119 cm −1 definitely do not correspond to vibrations of A 2 symmetry type. We have paid special attention to these extra bands that appear in LiNbO 3 single crystals Raman spectra despite the fact that they are prohibited by the selection rules. In order to do so, we have studied a number of lithium niobate single crystals, both nominally pure and doped, by Raman spectroscopy. We have assumed that some "extra" bands correspond to two-particle states of acoustic phonons with a total wave vector equal to zero. We have also detected a Zn concentration area (0.05-0.94 mol.% ZnO in a crystal) where doped crystal structure is more ordered: The order of alternation of the main, doping cations, and vacancies along the polar axis is increased, and oxygen octahedra are less distorted.Crystals 2019, 9, 535 2 of 37 changes. Features of the LN crystal structure determine features of its vibrational spectrum and many other physical characteristics. LN single crystal is a material with a widely developed secondary structure. It is important to note that the fine features of its structure and, accordingly, the physical characteristics can be significantly changed by changing the composition (changing the Li/Nb ratio and doping), as well as by changing the structure and physicochemical properties of the melt [3][4][5][6]. Moreover, the oxygen-octahedral structure allows doping of the crystal with high (several wt.%) concentrations of metals, as well as double and triple doping with different elements with different charge states.When interpreting the experimental results, the crystal should be considered as a solid solution of Me:Nb:LiNbO 3 (Me is a doping metal). Many metals are capable of entering the octahedral voids of the structure; the solubility limits of the metals are rather large. The concentration of doping metals in the crystal LN structure can reach several wt. % and accordingly~9 mol.% [2][3][4][5][6]. At the same time, the octahedral coordination of cations by oxygen ions allows significant geometric distortions of octahedra LiO 6 , NbO 6 , MeO 6 , O 6 , ( is a vacant octahedron) without changing their symmetry. This fact, along with a large number of point defects in the cation sublattice, leads to structural and optical ununiformity of LN crystal and to formation of complex ionic complexes and microstructures (clusters) in the main (primary) crystal structure, i.e., to the formation of a widely developed secondary crystal structure [6,[10][11][12][13]. By primary (basic) crystal structure we mean a structure that can be experimentally de...

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Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

“…They are also not dipole-active and do not experience LO-TO splitting [5,55,56]. However, A 2 symmetry type oscillations are allowed for the processes of hyper-Raman scattering [56].…”

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

Section: Particularities Of Raman Spectra Of Real Linbo 3 Crystals Wimentioning

confidence: 99%

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Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

2019

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The correlation between experimental polarized Raman spectra and their density functional theory prediction in the LCAO framework: The R3c LiNbO₃ crystal as a test case

Nogueira

Milani

Castiglioni

et al. 2021

J Raman Spectroscopy

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In this study, the polarized Raman spectra of the R3c LiNbO3 crystal are used as a benchmark test for density functional theory (DFT) full periodic boundary conditions linear combination of atomic orbitals (LCAO) calculation of the Raman tensors, according to the implementation in the CRYSTAL software. The theoretical approach used proved to provide excellent results regarding wavenumbers and relative intensities predictions for the transverse optical modes of both A1 and E symmetry, considerably improving over previously reported data based on the plane waves approach. Overall, the present investigation demonstrates that the LCAO approach, as implemented in the CRYSTAL software, gives excellent results regarding the calculation of Raman tensors and polarized Raman spectra. The possibility to put in correspondence the individual Raman tensors components and bands intensities in the different back‐scattering experimental configurations revealed that the computed Raman tensors are very accurate, not only considering their average values (tensors invariant in the combination suitable for the description of Raman scattering of isotropic materials) but also when the tensors individual components are considered. Based on the present results, a reassignment of the E (TO) modes of the R3c LiNbO3 crystal is proposed, in particular for the 2 E and 9 E modes, which have been a matter of discussion in the recent years.

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Raman activity of the longitudinal optical phonons of the LiNbO₃ crystal: Experimental determination and quantum mechanical simulation

Nogueira

Rérat

Fausto

et al. 2022

J Raman Spectroscopy

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In this study, the Y XX ð ÞY and the two equivalent Z XX ð ÞZ/Z YY ð ÞZ polarized Raman spectra of a LiNbO 3 single crystal have been recorded and used as a benchmark test for the density functional theory (DFT) calculation of the longitudinal modes and of their Raman activity. The theoretical approach, based on periodic boundary conditions and a linear combination of atomic orbitals (LCAO), provides excellent predictions of phonon wavenumbers and relative bands intensities for both A 1 and E Longitudinal Optical (LO) modes and complements a previous paper limited to the study of Transverse Optical (TO) modes. Overall, the present investigation demonstrates that the LCAO approach, as implemented in the CRYSTAL software, gives results of similar accuracy for the TO and the LO phonons features. By means of a band deconvolution scheme applied to the experimental spectra, we present, for the first time, a quantitative comparison between experimental and theoretically predicted polarized Raman band intensities of LiNbO 3 LO modes. This analysis highlights the role of the suitable determination of the static and highfrequency dielectric matrices that are needed for the prediction of the TO/LO frequency split but also the first nonlinear electric susceptibility tensor for an accurate description of the Raman intensity pattern.

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Raman scattering by longitudinal and transverse optical vibrations in lithium niobate single crystals

Cited by 33 publications

References 4 publications

Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

The correlation between experimental polarized Raman spectra and their density functional theory prediction in the LCAO framework: The R3c LiNbO₃ crystal as a test case

Raman activity of the longitudinal optical phonons of the LiNbO₃ crystal: Experimental determination and quantum mechanical simulation

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Raman scattering by longitudinal and transverse optical vibrations in lithium niobate single crystals

Cited by 33 publications

References 4 publications

Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

Raman Scattering in Non-Stoichiometric Lithium Niobate Crystals with a Low Photorefractive Effect

The correlation between experimental polarized Raman spectra and their density functional theory prediction in the LCAO framework: The R3c LiNbO3 crystal as a test case

Raman activity of the longitudinal optical phonons of the LiNbO3 crystal: Experimental determination and quantum mechanical simulation

Contact Info

Product

Resources

About

The correlation between experimental polarized Raman spectra and their density functional theory prediction in the LCAO framework: The R3c LiNbO₃ crystal as a test case

Raman activity of the longitudinal optical phonons of the LiNbO₃ crystal: Experimental determination and quantum mechanical simulation