The bond force constant and bulk modulus of C60

Computations of the bulk modulus (B) of the C60 molecule have been conducted by using density functional theory (DFT) and finite element analysis (FEA). The accuracy of an FEA approach to calculate the bulk modulus of the C60 molecule is evaluated by considering ab initio computations based on DFT as a reference. DFT predicts a value of the bond force constant of kr = 691 N/m and a strong influence of this parameter on the FEA predictions of B is found. DFT predicts the numerical value of B as 874 and 759 GPa, depending if the molecule is considered as a solid truncated icosahedron or a solid sphere; the corresponding values of B calculated by FEA are within 5.3% difference with respect to DFT. The relevance of considering a shell model as well as of using the detailed equilibrium coordinates of C60 in FEA calculations is assessed. The atomistic FEA is reliable for the calculation of bulk modulus of the C60 molecule, as long as the bond force constant is accurately known.