Vibrational modes of chalcopyrite CdGeAs2 crystal

•We get the phonon frequencies and their symmetry assignments of CdGeAs2 by first-principles calculations.•The low-temperature polarized-Raman-scattering spectra of CdGeAs2 crystal were obtained.•Comparing with the calculations, Raman active vibrational modes have been identified.•We give a systematic analysis and deduce effective charge and dielectric constants.

The optical-phonon spectra of CdGeAs2 were investigated by low temperature polarized Raman scattering. According to vibrational modes of ZnS-type materials and selection rules of Raman scattering, all Raman active vibrational modes in the Brillouin-zone (BZ) center of CdGeAs2 predicted from group-theory arguments were identified and artificially grouped in three energy bands, including 45–94, 158–215 and around 260 cm−1. Based on the Lyddane-Sachs-Teller (LST) relation and measured refractive indices, the low-frequency dielectric constant ε(0) is estimated to be 15.04 and shows good agreement with the previous tests and predictions.

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