Shape and size dependent thermophysical properties of nanocrystals

A theoretical model based on thermodynamic variables is employed in the present work to study the thermophysical properties of nanomaterials of different shapes and sizes. The model proposed by Qi and Wang [19] is applied to determine the cohesive energy of nanomaterial. The number of atoms on the surface to the total number of atoms in nanosolid is considered in terms of shape factor (α) and size of nanocrystal. The variation of cohesive energy (Ecn ), melting temperature (TmN), Debye temperature (θDN), Specific heat capacity (CpN), and Energy band gap (EgN ) is studied for spherical, regular tetrahedral, regular hexahedral and regular octahedral nanocrystals. The cohesive energy, melting temperature and Debye temperature are found to decrease as the grain size is reduced. However, the energy band gap and specific heat capacity are found to increase with decrease of grain size of nanomaterial. The results achieved in the present study are compared with the available experimental and also with those calculated from other theoretical models. The consistency between the present calculated results and the results reported earlier confirms the validity of the present model theory to explain the shape and size dependence of thermophysical properties of nanomaterials.