Infrared absorption in Phonon Harmonic Software ver. 6.15

The infrared absorption depends on effective charges, and is calculated for polarized or unpolarized light. The electric field splits the infrared active phonon modes to TO or LO components, and correspondigly assigns the intensities to these peaks. The TO mode frequencies and peak intensities do not depend on the crystal orientation, while those of LO modes change frequecies with phonon wavevector and intensities depends on the polarization of the incident infrared beam. The infrared absorption on polycrystal is computed by averaging the scattering spectra over many random polarization and crystal orientations. Such an averaging does not influence the TO phonon modes, but changes the LO peaks to bands. Symmetry of each mode or band is determined in Phonon.

FIGURE.1. Plot of infrared absorption spectra on polycrystalline tetragonal non-centrosymmetric Akermanite Ca2MgSi2O7. (a) Spectra were calculated by Phonon Software without any applyied broadening. (b) Measured spectra from Reference of J.Hanuza, M.Ptak, M.Maczka, K.Hermanowicz, J.Lorenc, A.A.Kaminskii, J.Solid State Chemistry, 191, 90 (2012).

Last update: July 20, 2014