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Raman activity of the longitudinal optical phonons of the LiNbO 3 crystal: Experimental determination and quantum mechanical simulation
Author(s) -
A. Nogueira Bernardo,
Rérat Michel,
Fausto Rui,
Castiglioni Chiara,
Dovesi Roberto
Publication year - 2022
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.6426
Subject(s) - raman spectroscopy , phonon , linear combination of atomic orbitals , atomic orbital , deconvolution , crystal (programming language) , wavenumber , molecular physics , raman scattering , transverse plane , density functional theory , optics , computational physics , physics , chemistry , condensed matter physics , computational chemistry , quantum mechanics , electron , structural engineering , engineering , computer science , programming language
Abstract In this study, the Y XX Y ¯ and the two equivalent Z XX Z ¯ / Z YY Z ¯ 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 high‐frequency 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.