The bulk modulus of fullerene C20 in the case of nonlinear volumetric deformation

The bulk modulus is one of the most important properties of fullerenes. This parameter indicates the volumetric deformation under the influence of external pressure. Therefore, the strength of fullerene can be interpolated from its bulk modulus. The strength of fullerene is often measured indirectly through its vibration frequency (a non-destructive measurement method). The vibration frequency of this fullerene family structure is determined by various methods such as Raman spectroscopy, finite element analysis, quantum chemistry, etc. However, these experimental results need theoretical explanation. In this paper, the authors present an approach from molecular dynamics. Most previously published works on the mechanical properties of fullerene are limited to the case of linear deformation (small deformation). This paper aims to establish the expression of the bulk modulus of C20 fullerene in both linear and nonlinear deformation cases. The results of this study demonstrate that the bulk modulus depends on the volume of fullerene in the case of large volumetric deformation (nonlinear case). In the literature on this issue, the bulk modulus of fullerene is considered constant when deformed. Therefore, the bulk modulus of C20 fullerene can be determined based on the volumetric strain rate and bond stiffness value. Additionally, the study also demonstrates that the bulk modulus of C20 fullerene is directly proportional to the bond stiffness value and inversely proportional to the volume of fullerene. Finally, the comparison between the bulk modulus value of C20 fullerene obtained in this study and other values obtained through Finite Element Analysis (FEA) and Density Functional Theory (DFT) verifies the accuracy of the study