Vibrational spectra and phonon dispersion relations
IR and Raman vibrational spectra (phonon eigenfrequences at Gamma point) are calculated either using classical lattice dynamics approach (GULP program), or for smaller periodic system using ab initio quantum mechanical approach within Density Functional Theory framework (Crystal, VASP). Vizualitations and animations are prepared using JMol package.
Phonon dispersion relations are calculated using VASP combined with Phonopy program. Some example results are presented below.
Fig. 1. Na-SOD (left) and Na-LTA (right) far IR spectra: comparison with experiment [1,2].
Fig. 2. Visualization of selected normal modes of vibration: Na-LTA (left), carbon clathrate Mg8C46 (right) [3,4].
Fig. 3. Decomposed FIR spectra of Mg2Si (left) and Mg2Si0.98Bi0.02 (right) [5].
Table 1. Calculated and measured positions of selected bands in FIR spectra of bismuth doped Mg2Si [5].