Raman spectra of fine-grained materials from first principles

• Published in: npj computational materials Vol. 6; no. 1
• Main Authors: Popov, Maxim N., Spitaler, Jürgen, Veerapandiyan, Vignaswaran K., Bousquet, Eric, Hlinka, Jiri, Deluca, Marco
• Format: Journal Article Web Resource
• Language: English
• Published: London Nature Publishing Group UK 14.08.2020; Nature Publishing Group
• Subjects: 639/301/1034/1037; 639/301/1034/1038; Automation; Barium titanates; Characterization and Evaluation of Materials; Chemistry and Materials Science; Computational Intelligence; Computer simulation; Crystals; DFT; Electric fields; Ferroelectric materials; Ferroelectricity; First principles; Group theory; Lattice vibration; Lithium niobates; Materials Science; Mathematical and Computational Engineering; Mathematical and Computational Physics; Mathematical Modeling and Industrial Mathematics; Physical, chemical, mathematical & earth Sciences; Physics; Physique; Physique, chimie, mathématiques & sciences de la terre; Polycrystals; Raman spectra; Raman spectroscopy; Relaxor; Single crystals; Spectrum analysis; Tensors; Theoretical; Vibrations
• ISSN: 2057-3960; 2057-3960
• DOI: 10.1038/s41524-020-00395-3

Raman spectroscopy is an advantageous method for studying the local structure of materials, but the interpretation of measured spectra is complicated by the presence of oblique phonons in polycrystals of polar materials. Whilst group theory considerations and standard ab initio calculations are helpful, they are often valid only for single crystals. In this paper, we introduce a method for computing Raman spectra of polycrystalline materials from first principles. We start from the standard approach based on the (Placzek) rotation invariants of the Raman tensors and extend it to include the effect of the coupling between the lattice vibrations and the induced electric field, and the electro-optic contribution, relevant for polar materials like ferroelectrics. As exemplified by applying the method to rhombohedral BaTiO 3 , AlN, and LiNbO 3 , such an extension brings the simulated Raman spectrum to a much better correspondence with the experimental one. Additional advantages of the method are that it is general, permits automation, and thus can be used in high-throughput fashion.