Abstract
The phase diagram of a Lennard-Jones system was estimated using conventional NPT molecular dynamics (MD) simulations. The standard cyclic boundaries were assumed. An elongated unit cell with both solid and fluid sections was found to be suitable as a model during the NPT MD simulations when calculating both the melting and vapor pressure curves. This unit cell contained 1000 molecules, of which, in the initial state, half were assigned to an FCC structure while the remainder had a density close to that of the critical state. The results of these simulations were compared with those of phase-1/phase-2 coexistence simulations and also with reported experimental data. The triple point was obtained by NVE MD calculations based on a unit cell containing both solid and gaseous sections, while the critical point was estimated by NVE MD using an elongated unit cell with a density near the critical value. Sublimation pressure was calculated by NVT MD with a unit cell again containing both solid and gaseous sections.
