Molecular dynamics simulations of nanocarbons at high pressure and temperature

A molecular dynamics study of carbon nanoparticles (980 and 10,034 atoms) under high temperature (1000–7000 K) and high pressure (2–45 GPa) has been made using the reactive LCBOPII potential. The most stable structure of the small cluster is onion-like (encapsulated fullerenic) on the whole pressure range, whereas a transition from onion-like to nanodiamond is observed for the big cluster as pressure increases from 2 to 45 GPa. The melting mechanism depends on the structure, initiated in the core in the case of an onion cluster and at the surface for the nanodiamond. A schematic phase diagram is proposed, that takes into account the finite size effects.