Phonon spectra of Cu_{6}PS_{5}Br superionic ferroelastic: experimental and theoretical studies

Abstract

The anomalous temperature behavior of the Raman scattering bands at superionic phase transition of Cu 6 PS 5 Br is revealed. Using density functional perturbation theory within local density approximation, ab initio long-wavelength phonons have been obtained for high-symmetry cubic structure. In the calculated phonon spectrum two unstable modes indicate the experimentally observed sequence of ferroelastic and superionic phase transitions.

Enhancement of Power Factor for Inherently Poor Thermal Conductor Ag8GeSe6 by Replacing Ge with Sn

“…Near phase transition ∼333 K (for Ag 8 GeSe 6 ) and ∼363 K (for Ag 8 SnSe 6 ), the full width at half-maximum (fwhm) for Se−Se vibrational mode decreases, while the Raman intensity enhances because of significant increase in vibration amplitude of Ag atom. 43 For Ag 8 GeSe 6 , Se−Se atoms vibrational mode emerges as most intense peak at 333 K, which suggest a metastable state at transition. The rise in vibrational amplitude near phase transition enables the hopping of Ag atoms.…”

Model research of phonon spectra of argyrodites family

“…Analysis of the crystal structures typical for the argyrodite family has revealed high variability in the number of crystallographic positions and in the occupancy factors [8]. In our previous paper [9], for ab initio calculations of the phonon frequencies in the Γ point of the Brillouin zone of the Cu 6 PS 5 Br crystal, we have chosen the crystal structure model with the coordinates and occupancies presented in Table 1. In this paper, the same model was used for calculations of the dispersion dependences of the phonon spectrum in the Brillouin zone [8].…”

Model Calculations of the Phonon Dispersion Curves for Cu6AsS5I Superionic Crystal

“…The performed analysis of the Cu 6 AsS 5 I crystal structure indicates a significant change in population densities of several crystallographic positions, therefore, model studies can use the framework for Cu 6 PS 5 Br isostructural crystal that was proposed in previous Refs. [7,8]. Such a crystal structure, according to the Ref.…”