Effect of phonon frequencies on specific heat of ZnO nanostructures

Abstract

The temperature dependent specific heat Cp of Zno nanostructures is studied using phonon frequency mechanism. Softening of phonon frequencies at interfaces in nanostructures is considered as the main reason of enhancement in Cp. Phonon specific heat is estimated using the Debye model which is obtained following an overlap repulsive potential. In nanostructures, having large interface volume ratio, the phonon frequencies and Debye temperature are less at the interfaces than at the core of nanocrystal. The contributions to specific heat due to atoms present at interfaces (CIF) and atoms present at the core of nanostructure (CNC) are estimated separately by estimating the characteristic Debye temperature (θD) using elastic force constant (κ) to find the total phonon contribution. The temperature derivative of the internal energy yields the electronic contribution to specific heat (Cel).