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.Comment: 8 pages, figure

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The results of the high-field technique for obtaining and testing the carbyne strength in situ are presented. By using molecular dynamics simulation and ab initio calculations, a comprehensive analysis of the results is executed. High-field technique for experimental measurement of the carbyne strength in situ is briefly described. It is shown that the technique used gives a lower estimation for strength of carbyne, which equals 251 GPa at T = 77 K. This value is close to the strength 7.85 nN (250 GPa) of contact atomic bond between carbyne and graphene sheet, from which the monatomic chain is pulled. The strength of carbyne itself is determined by strength of an edge atomic bond and it is ≈ 12.35 nN (393 GPa) at T = 0 K. For carbynes containing more than 10 to 12 atoms, the coefficient of elasticity (kY = 145.40 nN) and the elastic modulus (Y = 4631 GPa) are ascertain.

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