Lattice dynamics of CoO from first principles

Cobaltous oxide (CoO) has been studied by using density-functional theory and the generalized-gradient approximation with correction for Hubbard energy. The calculated electronic structure indicates that CoO is a charge transfer insulator since the Co 3d and O 2p states are strongly hybridized. The calculated band gap and the spin magnetic moment on divalent Co are in good agreement with the experimentally observed values. The so-called direct method based on calculated Hellmann-Feynman forces is used to obtain the density of states and the dispersion relations of phonons. The temperature dependence of the mean-squared vibrational amplitudes and the behavior of the lattice contribution to heat capacity are analyzed and discussed in the framework of the harmonic approximation. The results of calculations agree with the existing theoretical and experimental data.