Polarized Raman Study of Internal Vibrations of the Organic Cation in 3-Cyanopyridinium Lead Tribromide Post-perovskite

Abstract

In this work, we apply polarized Raman spectroscopy for study of internal vibrations of the 3-cyanopyridinium cation in the halide post-perovskite (3cp)­PbBr3 (3cp = 3-CN-C5H5NH+). For a single cation, the vibrational frequencies and intensities of the Raman signal were calculated using the density functional theory. Selection rules were established for vibrations of cations in the crystal. These rules together with modeling results were used to identify the internal vibrations of the cation in the Raman spectrum of the crystal. Narrow and isolated internal vibrations of cations could be used as spectators of the crystalline environment.

Cluster approach for the density functional theory study of organic cation vibrations in hybrid halide post‐perovskite 3‐cyanopyridinium lead tribromide

“…The synthesis and basic characterisation of (3cp) PbBr 3 post‐perovskite single crystals are given in previous studies 24,25 . The experimental Raman spectrum of post‐perovskite (3cp)PbBr 3 was measured at T = 300 K using a Horiba LabRam HR 800 spectrometer with a grating of 1800 mm −1 and a spectral resolution of 2 cm −1 .…”

“…The unpolarised Raman spectrum was recorded. A detailed study of polarised Raman spectra and the selection rules used for their interpretation is given in our recent paper 25 . DFT calculations were performed using the GAUSSIAN16 program 26 installed on the Huawei cluster in the Computing Center of St. Petersburg State University (cc.spbu.ru).…”

“…The DFT was used earlier to address the properties of cations in this material. DFT of isolated cation was used to establish the vibrations selection rules and to identify vibrations in the Raman spectrum of the material 25 . The cluster consisting of two cations (dimer) was used to evaluate the inter‐cation interaction manifesting itself as an emergence of the organic band in crystal DFT study 24 .…”

Internal Vibrations of Pyridinium Cation in One-Dimensional Halide Perovskites and the Corresponding Halide Salts

“…To study the organic subsystem of hybrid halide perovskites, neutron [ 9 ] and X-ray diffraction (XRD) [ 9 , 10 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ], solid-state nuclear magnetic resonance (NMR), quasielastic neutron scattering (QENS) [ 14 , 15 , 16 , 17 ], Raman [ 10 , 11 , 12 , 13 , 21 , 22 , 23 , 24 , 33 ] scattering methods and density functional theory (DFT) modeling [ 22 , 31 , 34 ] are widely used. The vibrational properties of inorganic perovskite frameworks have been studied in the literature [ 5 , 10 , 21 , 23 ].…”

“…Organic cations are spectators of the crystalline environment [ 22 , 35 ]. The polarized Raman spectroscopy of organic vibrations could be used to determine the crystal orientation [ 33 ] and the cation movement [ 20 ].…”