Optical phonons of $NdBaCo2O5+x$⁠: lattice dynamicscalculations

Optical phonons (k≈0) of the double perovskite $NdBaCo2O5+x$ are calculated in the cases of $x = 0,$ 1 (tetragonal $P4/mmm,$ $a = b = ap,$ $c≈2ap$⁠) and $x = 0.5$ (orthorhombic Pmmm, $a = ap,$ $b≈2ap,$ $c≈2ap$⁠) using the shell model. The calculated modes in the three crystal structures are classified according to their symmetry and frequency. By analyzing the eigenvectors for different modes the most intense bands in the Raman spectra of the complex compound $NdBaCo2O5+x$ are predicted.