Fig. 3: Two-phase AIMD and MLMD simulations for determining metastability.
Two-phase AIMD and MLMD results for the stability of polymeric amorphous material pa,rc[CO + O2]. Visualization of the a initial and b final atomic configurations along a 624-atom two-phase simulation trajectory (432 atoms initially in pa,rc[CO+O2] and 192 atoms in molecular m[CO+O2] at P = 1.6 ± 0.6 kbar and T = 300 K. Oxygen and carbon atoms are shown in red and brown, respectively. c Radial distribution function, g(r), for the initial (top) and final (bottom) configurations. The latter is averaged over simulation time of 5.7 ps, after equilibrating for over 3.1 ps. The insets show the polymeric g(r) features that do not alter significantly during the course of the simulation. d Computed pressure during the AIMD simulation run is shown to remain at 1.6 ± 0.6 kbar. The 15,600-atom configurations at e the initial and f the final (after 100 ns) stages of an MLMD run, together with the associated radial distribution functions g(r), demonstrating the stability of the recovered amorphous structure at larger length and time scales. g Computed pressure during the MLMD simulation, showing to equilibration at 1.9 ± 0.3 kbar. h Mean square displacements of C and O atoms from the gaseous and polymeric phases during the MLMD run, demonstrating the stability of the latter. i Parity plots of energy and forces for the machine-learned interatomic potential (MLIP), with RMSE values indicated. j Normalized vibrational density of states (VDOS) for AIMD (over 8.8 ps), MLMD (over the first 8.8 ps), and MLMD (over the entire 100 ns).
