Ab initio vibrational and dielectric properties of chalcopyrite CdGeAs2

We have performed a first-principles study of structural, vibrational and dielectric properties of CdGeAs2. The calculations have been carried out within the local density functional approximation using norm-conserving pseudopotentials and a plane-wave basis. Calculations of the zone-center optical-mode frequencies (including longitudinal-optical/transverse-optical splitting), Born effective charge tensors for each atom, and dielectric constants, using density functional perturbation theory, are reported. The fully relaxed structural parameters are found to be in good agreement with experimental and other calculation data. All optical modes are identified and agree with infra-red and Raman measurements. (c) 2011 Elsevier Masson SAS. All rights reserved.