  The superior electronic, optical and magnetic properties of carbyne have been
called for optoelectronic and magnetoelectronic applications. However,
manufacturing a monoatomic chain of more than 6000 carbon atoms presents a huge
technical challenge. In order to predict the optimal chain length in different
environments, we develop a Monte Carlo model in which a finite-length carbyne
in the size of 4000-15000 atoms is encapsulated by a carbon nanotube at finite
temperatures. Our Monte Carlo simulation shows that the stability of the
carbyne-nanotube is influenced by the charity and porosity of carbon nanotube,
external pressure, temperature and the chain length. When the geometric
structure of carbon nanotube and environmental parameters are provided, our
Monte Carlo algorithm can predict the maximum length of the internal carbyne.
Our work presents a path to manufacture a carbon chain much longer than 6000
atoms at room temperature.
