Interatomic forces breaking carbon-carbon bonds

We compare computational methods for determining the force between carbon atoms as a function of bond length, in order to establish which ones are capable accurately simulating carbon-carbon bonds breaking due applied mechanical strain nanomaterials. Results from Tight-binding, density-functional theory and molecular mechanics potentials compared Møller-Plesset perturbation complete-active-space self-consistent-field method through application small molecules. Of two three tight-binding parameter sets chosen only DFTB3 gives results broadly similar those first-principles methods; others fail give physically meaningful variation forces with internuclear separation. This then periodic nanoribbon under tensile strain. The even qualitatively reproduce single catastrophic failure shortly after peak stress indicated by DFTB3. shows importance electronic behaviour interatomic relevant determination strength materials at atomic-length scales.