Evolution of the energetics for our 150 M_⊙ and 250 M_⊙ models. We show the kinetic energy (blue, circles), the binding energy (green, times) that is the sum of gravitational and thermal energies, and the nuclear binding energy (red) of the stars. Here, the nuclear binding energy is defined by the difference between the total nuclear binding energy of all nuclei at the end of carbon burning and that of a given evolutionary epoch (see description in the text). The zero point in time is defined as the time of the beginning of pair-instability explosion.