Nanocomposites and nanomaterials

Lifetime of carbyne-graphene nanoelements
S. Kotrechko1,2, A. Timoshevskii1, E. Kolyvoshko2 , N. Stetsenko1 , 
Yu. Matviyvhuk1
1 G.V. Kurdyumov Institute for Metal Physics, National Academy of Sciences of Ukraine, Vernadsky Blvd.,36, Kyiv-03680, Ukraine.
E-mail: natusjaimp@gmail.com
2 Taras Shevchenko Kyiv National University, Volodymyrska Street, 64/13, Kyiv-01601, Ukraine.
Specific feature of the current state of nanophysics and nanotechnology is the transition from finding nanostructures with exceptional properties and developing technologies for their manufacture, to the practical use of these properties in nanoelements and nanoproducts. At this stage, their lifetime in the conditions of operation in products comes to the fore. The key factors that limit the lifetime are high temperatures, force field, electric and magnetic fields. 
The aim of the report is to analyze the main physical effects that govern the instability and break of bonds in separate carbyne chains and carbyne-graphene nanoelements (CGNs), consisting of graphene sheets connected by carbyne chains. In general, these effects are inherent in nanoelements and nanocomposites consisting of one- and two-dimensional nanostructures.
Based on the results of the first-principle (DFT) calculations, MD-simulation and statistical analysis, the key factors that govern the lifetime of studied objects were found, namely:
•	Existance of an "instability zone" (IZ). The lifetime of nanoelement essentially depends on the IZ parameters. If the magnitude of the acting force exceeds the IZ lower limit, then there is a synergism of the effect of the force field and temperature on the lifetime. As a result, the lifetime of nanoelements may be reduced by tens of orders of magnitude. The report considers the phenomenon model and gives a prediction of the thermal-force conditions for synergism.
•	Quantum mechanical effect include the dependence of the lifetime value on whether the number of atoms in carbyne chain is even or odd ("even-odd" effect). This effect is the result of existence of an "even-odd" effect for the contact bond  strength and biding energy. Besides, there is an inversion of this effect under the mechanical loading.
The report considers the fluctuation model of CGNs’ instability and lifetime, offered by authors, which enables to predict their lifetime within a wide range of values of thermomechanical loading.
Within the framework of the proposed approach, the regions of temperatures and of mechanical loads are found, where the practical use of CGNs is possible.

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4.	S. Kotrechko, A. Timoshevskii, E. Kolyvoshko, Yu. Matviychuk, N. Stetsenko and B. Zhang. Lifetime of carbyne-based nanodevices: size and “even-odd” effects // Eur Phys J Plus. – 2019.- 134: 182 P. 1-10.