  We present a density functional perturbation theory approach to estimate the
transition temperature of the charge density wave transition of TiSe2. The
softening of the phonon mode at the L-point where in TiSe2 a giant Kohn anomaly
occurs, and the energy difference between the normal and distorted phase are
analyzed. Both features are studied as function of the electronic temperature,
which corresponds to the Fermi-Dirac distribution smearing value in the
calculation. The transition temperature is found to be 500 K and 600 K by
phonon and energy analysis, respectively, in reasonable agreement with the
experimental value of 200 K.
