The origin of complex behavior of liquid carbon: an insight from computer simulation

TL;DR

It is shown that within the framework of this model carbon demonstrates a relatively low critical temperature, which can affect the results of experimental measurements of melting point of graphite.

Abstract

In the present paper we perfomrm molecular dynamics simulation of liquid carbon with a machine-learning potential GAP-20. We show that within the framework of this model carbon demonstrates a relatively low critical temperature, which can affect the results of experimental measurements of melting point of graphite.

Figures (6)

• Figure 1: Boiling curve of carbon obtained by the corresponding states law with the critical parameters from Ref. leider in (a) $\rho - T$ and (b) $P-T$ planes. The red star in the panel (b) shows an extrapolation of the boiling curve to the limit of zero pressure. The curves 'Bundy' and KSCh in the panel (b) show the melting curves of graphite from Refs. bundy and ksch correspondingly.
• Figure 2: Equation of state and fitting curve of GAP-20 model of carbon at (a) $T=4100$ K, (b) $T=4400$ K and (c) $T=5000$ K.
• Figure 3: Several isotherms next to the critical temperature of carbon obtained from the polynomial fit.
• Figure 4: A snaphot of a sample at $T=4100$ K and $\rho=1.55$$g/ml$. Traces of crystallization are visible in the bottom part of the Figure.
• Figure 5: (a) Isobaric heat capacity, (b) thermal expansion coefficient and (c) isothermal compressibility of GAP-20 model of carbon next the critical point.