▎ 摘　　要

Stretching (k(r)) and bending (k(theta)) bond force constants appropriate to describe the bond stiffness of graphene and benzene are calculated using density functional theory. The effect of employing different exchange-correlation functionals for the calculation of k(r) and k(theta) is discussed using the generalised gradient approximation (GGA) and the local density approximation (LDA). For benzene, k(r) = 7.93 mdyn angstrom(-1) and k(theta) = 0.859 mdyn angstrom rad(-2) using LDA, while k(r) = 7.67 mdyn angstrom(-1) and k(theta) = 0.875 mdyn angstrom rad(-2) using GGA. For graphene, k(r) = 7.40 mdyn angstrom(-1) and k(theta) = 0.769 mdyn angstrom rad(-2) using LDA, while k(r) = 6.88 mdyn angstrom(-1) and k(theta) = 0.776 mdyn angstrom rad(-2) using GGA. This means the difference between the bond force constants for benzene and graphene can be as large as similar to 12%. The comparison between these two systems allows for elucidation of the effect of periodicity and substitution of carbon atoms by hydrogen in the stiffness of C-C bonds. This effect can be explained by a different redistribution of the charge density when the systems are subjected to strain. The parameters k(r) and k(theta) computed here can serve as an input to molecular mechanics or finite element codes of larger carbon molecules, which in the past had frequently assumed the same bond force constants for graphene, benzene or carbon nanotubes.