First-principles Raman studies on rare-earth carbide halides

We have investigated the zone-center Raman modes of Y2C2Br2 and Y2C2I2 by first-principles calculations based on density functional theory. The phonon frequencies are determined by carrying out total-energy and atomic-force calculations using the full-potential linearized augmented plane-wave (LAPW) method. The Raman intensities are obtained from the derivative of the dielectric function with respect to the normal coordinates of the phonons. We find excellent agreement with previously measured Raman spectra.