Theoretical and experimental vibrational spectra of ReSe2 nanocrystals, synthesized by self‐limited chemical vapor deposition (CVD), are reported. Scanning electron microscopy reveals that the nanocrystals have the shape of polygon nanoplates (NPs), 20 nm thick and about 100–300 nm wide. X‐ray diffraction studies determined their triclinic structure (space group, P‐1 [no. 2]). The wavenumbers of the Raman‐ and infrared (IR)‐active phonon modes were calculated using the density functional perturbation theory (DFPT), along with the dispersion curves and phonon density of states. The set of theoretical phonon wavenumbers is found to correlate well with the experimental Raman and IR spectra. We established that, unlike ReS2, ReSe2 does not exhibit a “phonon gap.” Several “extra” bands in the experimental Raman spectrum of ReSe2 are argued to be defect‐induced contributions of phonons from F and Q critical points of the Brillouin zone. In addition, the effect of Fermi resonance is observed in the Raman spectrum of the ReSe2 NPs, which manifests itself in an increase of the intensity of second‐order bands due to their interaction with first‐order phonons.

In this work, the effect of electric field induced by localized plasmon excitation in nanostructured metal film on the vibrational spectrum of adsorbed organic molecule is studied theoretically. By using the Green function formalism, we show that electric field can significantly influence both the frequencies of the molecular vibrations and the anharmonicity constant. Consequently, if Fermi resonance can take place in the adsorbed molecule, it is spectral manifestation (in Raman spectra) will also be modified by the electric field of plasmon. We illustrate the effect with a CO2 molecule adsorbed on nanostructured gold surface, a situation relevant to the application of Surface‐Enhanced Raman Scattering (SERS) or other plasmon‐mediated phenomena. The obtained in these work analytical expressions are shown to describe well spectral features in earlier experimental SERS studies on CO2.

Phonon spectra of two novel nonlinear optical crystals, PbGa2GeSe6 and PbGa2GeS6, are studied experimentally by Raman and infrared reflection spectroscopy and theoretically by density functional theory (DFT) lattice dynamics calculations. The experimental peak frequencies are compared with calculated vibration frequencies, and a very reasonable agreement is established. A comparative analysis of results for PbGa2GeSe6 and PbGa2GeS6 with earlier reported data on relevant binary and ternary metal chalcogenides clearly indicates that the similarity of their phonon spectra stems from the presence of GeS4 and GeSe4 tetrahedra as structural building blocks.