State-to-state and direct molecular simulation study of energy transfer and dissociation of nitrogen mixtures

This work presents a comparison of the non-equilibrium dissociation and energy transfer processes predicted using the state-to-state (StS) and direct molecular simulation (DMS) methods. The StS method is a deterministic method, which relies on pre-computed kinetic data used in the master equation for each rovibrational energy state. The DMS method is a stochastic interpretation of molecular dynamics, directly tracking the changes in energy of particles due to collisions. Using both methods we study a simple zero-dimensional heat bath in which initially cold nitrogen molecules are instantaneously heated to between 5 000 K and 20 000 K. To isolate the effect of the N₂-N collision processes, we ignore any reactions due to collisions between two molecules. We find that both methods are in excellent agreement in the temperature range studied, with both macroscopic (composition and average internal energies) and microscopic (distribution of internal energy states) properties matching throughout the energy transfer and dissociation processes.