Thermal nonequilibrium relaxation of methane-nitrogen system investigated by state-resolved deep-potential-energy molecular dynamics

YX Hu and CM Guo and HW Song and JY Ma, PHYSICAL REVIEW A, 111, 062821 (2025).

DOI: 10.1103/2hfd-1zfq

Direct molecular simulation and the state-to-state method, as the prevailing theoretical approaches for studying thermally nonequilibrium molecular collisions, strongly rely on available high-precision potential energy surfaces and extensive trajectory calculations, and their application to polyatomic molecular systems remains a challenge. In this paper, the state-resolved deep potential molecular dynamics (SR- DPMD) method is proposed, which performs potential energy surface construction and molecular dynamics simulation based on the deep potential molecular dynamics scheme and then achieves energy state resolution during the simulation through normal mode analysis. Applying this method to the simulation of thermal nonequilibrium dynamics of the methane-nitrogen system and comparing it with the simulation of state- resolved ReaxFF, combining the energy state analysis of five-atom molecules is realized. The results demonstrate that vibration-rotation coupling and vibration-vibration coupling can directly affect the vibrational energy relaxation behavior of molecules. It is evident that the accuracy of the ReaxFF is inadequate to facilitate the energy state resolution of the molecule; however, it is capable of yielding qualitative outcomes concerning the energy relaxation of the molecule during the simulation. Overall, the SR-DPMD method provides a powerful tool for understanding the energy state evolution of polyatomic molecules under nonequilibrium conditions and is expected to provide valuable insights into energy relaxation, chemical reactions, and their coupling processes. The reaction force field is also dedicated to providing new perspectives for the study of thermal nonequilibrium dynamics.

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