Atomic structure and mechanical properties of carbyne

The atomic structure and mechanical properties of the carbyne (monatomic linear chains), containing from 2 to 21 carbon atoms, are theoretically investigated by ab-initio methods. We demonstrate the existence of a stable cumulene-structure in the inner part of chains with the number of atoms N>=10. We present a general stress-strain diagram of chains until the moment when they break, which enables to determine their strength, elasticity and fragility. For chains with N>=4, the relationship between the strength of the chain and the binding energy of the edge atom in the chain is established. The existence of scale-effect and "even-odd" effect for such properties as strength, elasticity and fragility is observed. We demonstrate that the 5-atom carbon chains show the maximum strength value.