Structure and thermodynamic stability of carbon clathrates: A Monte Carlo study

Clathrates are strong, low density, fully sp3 structures that have been found for several elements of the IV group. Carbon clathrates however are, as of now, hypothetical materials. Ab initio calculations at T = 0 K predict carbon clathrates to be metastable with remarkable mechanical and electronic properties. Here we study the behavior and structural stability of the type I C46 carbon clathrates up to high temperature and pressure by means of Monte Carlo simulations based on an accurate model for the interatomic interactions. We find that the clathrate structure remains mechanically stable up to melting and we report the equilibrium structural parameters, thermal expansion, and equation of state.