Vibrational spectra and nonlinear optical coefficients of rhombohedral halide compounds with , Br, Cl
- Case Western Reserve Univ., Cleveland, OH (United States); California State Univ. (CalState), Long Beach, CA (United States)
- Case Western Reserve Univ., Cleveland, OH (United States)
The zone-center phonons are calculated here for rhombohedral CsGeX3 compounds with X=I, Br, Cl using density functional perturbation theory in a plane-wave pseudopotential method. The infrared absorption and reflection spectra are simulated and show that the absorption has a strong contribution from the LO as well asTO modes. Both the lowest and highest IR active modes have strong oscillator strengths for each symmetry (A1 and E) and correspond to motions of either the Cs or Ge ions relative to the halogen ions. respectively. The intermediate modes have low oscillator strength because their mode pattern shows less clearly a dipole pattern.The polarization dependent Raman spectra for various back scattering configurations are simulated. Only the highest modes of each symmetry have a strong Raman intensity. The findings for the Raman spectra are found to be in good agreement with the available experimental data for polycrystalline films when averaging over directions. The Born effective charges and high and low frequency dielectric tensors as well as the second-order nonlinear optical coefficients are calculated. The ratio of the static to the high-frequency dielectric constants are extremely high and analyzed in terms of the contribution of each mode to the Lyddane-Sachs-Teller relation. The nonlinear optical coefficients decrease strongly from I to Br to Cl in reverse order of the band gaps and are foundto be consistent with available experimental results
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- Grant/Contract Number:
- SC0008933
- OSTI ID:
- 1591889
- Alternate ID(s):
- OSTI ID: 1324020
- Journal Information:
- Physical Review B, Vol. 94, Issue 11; ISSN 2469-9950
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
Synthesis of Lead‐free CsGeI 3 Perovskite Colloidal Nanocrystals and Electron Beam‐induced Transformations
|
journal | May 2018 |
Similar Records
First-principles calculations of phonons and Raman spectra in monoclinic
superlattice for a model two-dimensional quantum Heisenberg antiferromagnet