The bond force constant and bulk modulus of C60

Computations of the bulk modulus (B) of the C-60 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 C-60 molecule is evaluated by considering ab initio computations based on DFT as a reference. DFT predicts a value of the bond force constant of k(r) = 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 C-60 in FEA calculations is assessed. The atomistic FEA is reliable for the calculation of bulk modulus of the C-60 molecule, as long as the bond force constant is accurately known. (C) 2013 Published by Elsevier B.V.