Potential energy surface of interaction of two diatomic molecules for air flows simulation at intermediate temperatures

The paper studies the potential energy surface (PES) of interaction between two rigid diatomic molecules (N2–N2, N2–O2, O2–O2). The dependence of energy on the angles of mutual orientation of the two molecules is carefully described (18000 DFT calculations for each pair) so that the obtained PES would be suitable for detailed simulation of the rotational excitation and relaxation in intermolecular collisions in air. The DFT results were fitted by proposed multi-particle interaction model with good accuracy. Corresponding force field was calculated and tested on two problems (simulation of the equilibrium state and the adiabatic rotational relaxation), its software implementation is attached to the paper and one can use it for molecular dynamics calculations.