Nanocomposites and nanomaterials

Atomic mechanisms governing stability and lifetime of carbyne-graphene nanoelements

S. Kotrechko1, A. Timoshevskii1, E. Kolyvoshko2, N. Stetsenko1, 
Yu. Matviychuk1
1 G. V. Kurdyumov Institute for Metal Physics, Natl. Acad. of Sci. of Ukraine, Vernadsky Blvd.,36, Kyiv-03680, Ukraine.
E-mail: serkotr@gmail.com
2 Taras Shevchenko Kyiv National University, Volodymyrska Street, 64/13, Kyiv-01601, Ukraine.

Carbyne-graphene nanoelements (CGNs) are currently considered as one of the main components of all-carbon-based nanodevices. These are graphene sheets joined by a monatomic chain of carbon atoms. Possibility to realise extraordinary functional properties of these elements for a long time is determined by the thermomechanical stability of the contact bond between the carbyne and graphene.
This report outlines ideas of the atomic mechanism of instability and break of contact bond in the CGNs. Main factors that govern their lifetime are ascertained.
Based on the DFT calculation findings, the existence of a bandgap for equilibrium states of atoms (ES bandgap) was established. This is a key factor that both controls the kinetics of contact bond break and pre-determines the lifetime of CGNs under mechanical stress. Quantum-mechanical properties of the ES bandgap are manifested in the dependence of its width on whether the number of atoms in carbyne chain is even or odd (“even-odd” effect). Nanoelements with "odd" chains have the maximum width the ES bandgap. Within the framework of the proposed fluctuation model of instability and contact bond break in the CGNs, regularities of the effect of temperature and force load on the lifetime of carbyne-graphene nanoelements were ascertained. The existence of an "even-odd" effect for life time is one of the specific features of above regularities. At mechanical load  (where  is contact bond strength) the lifetime of nanoelements with "odd" chains may exceed by an order of magnitude the corresponding values for "even" chains. In contrast, unloaded CGNs with "even" chains have a longer lifetime. The report presents dependences lifetime versus temperature and mechanical load for CGNs containing carbyne chains of different lengths. The temperature-force conditions and parameters for CGNs are ascertained, which provide the possibility of their use in nanodevices.

1.	Timoshevskii A., Kotrechko S., and Matviychuk Yu. Atomic structure and mechanical properties of carbyne // Phys Rev.-2015.- 91.-P. 245434 (9).
2.	Kotrechko S., Timoshevskii A., Kolyvoshko E., Matviychuk Y and Stetsenko N. Thermomechanical stability of carbyne-based nanodevice // Nanoscale Res Lett.-2017.- 12:327 P. 1-8.