Investigation of thermal evolution of copper nanoclusters encapsulated in carbon nanotubes: a molecular dynamics study.

Abstract

We have studied the heating and cooling processes of CuN nanoclusters encapsulated in CNTs with different diameters and chiralities in the range of 100-1700 K. We have investigated all of the possible effects: the effects of the nanocluster size, CNT diameter, and CNT chirality on the thermodynamic, structural, and dynamic properties during the melting process. Our thermodynamic results showed that the melting temperatures of the confined nanoparticles tend to increase with the nanoparticle size. Our energy results also showed that the melting temperature of the nanocluster decreases upon decreasing the CNT diameter, which is due to the greater nanocluster-CNT wall interactions in the smaller nanotube which make the cluster to expand more easily on the interface. The results also showed that the encapsulation of the nanocluster in the zigzag CNT has lower energy values than the armchair one, which is due to the greater interaction of the nanocluster and the zigzag CNT wall. We have also recognized a hysteresis in the course of the cooling process, which can be due to the fact that the nanoclusters and the nanotube make a coherent interface structure with more stability. Using the radial distribution function, it has been shown that the structural change with temperature is irreversible. Our dynamical results indicated that the bigger nanocluster has slower dynamics than the smaller cluster. It is also shown that the nanocluster on the smaller and zigzag CNTs has slower dynamics than the bigger and armchair tubes.