Phonons in nanocrystalline fcc nickel

The enhancement in the phonon DOS of nanocrystalline fcc Ni at low and high energies is due to the anisotropic changes in the interatomic force constants as compared to the bulk phase fcc Ni. The specific heat and vibrational entropy of nanophase is found to be greater than that of the bulk phase. There occurred a peak in the excessive specific heat of nanocrystalline fcc Ni at low temperatures. The excessive entropy of nanocrystalline Ni also has a peak at low temperatures but it becomes constant at high temperatures. The free energy of nanophase is lower than that of the bulk phase. The difference in the free energies of bulk phase and nanophase Ni increases linearly with temperature.