We used GAFF for all-atom MD simulations and employed a time-step of 2 fs, with all covalent bonds involving hydrogen atoms held rigid using the LINCS algorithm. We applied periodic boundary conditions with a single unit cell. Both the van der Waals and Coulomb potentials were cutoff at 1 nm with the potentialshift-Verlet modifier, and long-range Coulomb potential was calculated using particle mesh Ewald (PME). The velocity rescale thermostat was implemented for temperature coupling (tau-t = 0.1 ps for equilibration and 5 ps for production runs) whereas the Berendsen barostat was used for pressure coupling (tau-p = 1 ps for equilibration and 10 ps for production runs). Although this barostat slightly suppresses volume fluctuations, the fluctuations for this size system are not expected to affect the overall phase behavior.