Dynamical behavior and high-pressure study of C20@Tube peapod structure

The classical molecular dynamics (MD) method and density functional theory are utilized to study the dynamics and high-pressure behaviors of C20@Tube peapod structure. Results show that the critical and most suitable diameters of the tube for filling the C20 molecule are 9.5 and 10.86 Å, respectively. The mean free path and frequency of collision between the host and guest molecules are analyzed. Competition between the tube's confinement effect and the temperature on the molecular motion is studied. Two superhard carbon phases with a large bulk modulus are obtained under high pressure. The encapsulated C20 molecule induces a decrease in the band gap under ambient conditions and a lower pressure of closure of band gap. In addition, the application of pressure leads to a redistribution of electric charge between the host and guest molecule. The encapsulation induces a red shift of the vibrational optic modes for both the tube and the C20 molecule.