The mechanical strength of a covalent bond calculated by density functional theory

The rupture forces of covalent bonds in a polymer as a function of bond lifetime are calculated with an Arrhenius kinetics model based on high-level density functional theory calculations. Relaxed potential energy surface scans of small model molecules yield potential functions that account for the deformations and hybridizations caused by the application of force. Morse potentials chosen to exhibit the same well depth and maximum force are used as an analytic representation of an individual bond in an infinitely long one-dimensional polymer. Application of force deforms the potential, and the activation energy for the bond rupture event together with the frequency of an optical phonon in the one-dimensional polymer are the two Arrhenius parameters. Rupture forces of the bonds C-C, C-N, C-O, Si-C, Si-N, Si-O, and Si-Si are reported as a function of the lifetime of the bond. (C) 2000 American Institute of Physics. [S0021-9606(00)30617-1].