Understanding the phase separation of N-2/H2O and CO2/H2O binary systems through reactive force fields-based molecular dynamics simulations

L Lv and L Zhang and ML Yang, JOURNAL OF APPLIED PHYSICS, 124, 235901 (2018).

DOI: 10.1063/1.5066585

Phase separation has a considerable effect on the detonation performances of explosives, but its mechanism has seldom been studied in terms of the interatomic interaction through molecular modeling. The binary mixtures of molecular N-2, CO2, and H2O, which are the key components of detonation products of common explosives, with high density and at high temperature were investigated by using the reactive force fields-based molecular dynamics simulations. The mixing and demixing behaviors of N-2/H2O and CO2/H2O systems were compared to distinguish the driven forces of phase separation. The N-2/H2O mixtures with high density exhibit a remarkable phase separation at low temperature, while the CO2/H2O mixtures are mixing in a wide range of density and temperature. Similar changes in the repulsive van der Waals energy were found for all the studied systems. However, the corresponding changes in the attractive Coulomb energy are quite different for the mixing and demixing systems. Moreover, the polarization effect in dense systems contributes greatly to the Coulomb interaction. The Coulomb attraction is thus responsible for the phase separation of the dense systems under extreme conditions. Published by AIP Publishing.

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