Phonon spectrum of lead oxychloride Pb$_{3}$O$_{2}$Cl$_{2}$: Ab initio calculation and experiment

IR and Raman spectra of Pb$_{3}$O$_{2}$Cl$_{2}$ in the range of 50–600 cm$^{-1}$ have been detected for the first time. Ab initio calculations of the crystal structure and the phonon spectrum of Pb$_{3}$O$_{2}$Cl$_{2}$ in the framework of LCAO approach have been performed by the Hartree–Fock method and in the framework of the density functional theory with the use of hybrid functionals. The results of calculations have made it possible to interpret the experimental vibration spectra and reveal silent modes, which do not manifest themselves in these spectra but influence the optical properties of the crystal.