A study of Ar-N2 supercritical mixtures using neutron scattering, molecular dynamics simulations and quantum mechanical scattering calculations

The microscopic structure of Ar-N2 supercritical mixtures was obtained using neutron scattering experiments at temperatures between 128.4 and 154.1 K, pressures between 48.7 and 97.8 bar and various mole fractions. Molecular Dynamics simulations (MD) were used to study the thermodynamics, microscopic structure and single molecule dynamics at the same conditions. The agreement between experimental and theoretical results on the intermolecular structure was very good. Furthermore, a new explicitly-correlated coupled cluster potential energy surface was obtained for the Ar-N2 van der Waals complex. The ab initio potential energy surface (PES) was found to be in agreement with the MD interaction potential. The global minimum of the ab initio PES De = 98.66 cm−1 was located at the T-shaped geometry and at the intermolecular equilibrium distance of Re = 7.00a0. The dissociation energy of the complex was determined to be D0 = 76.86 cm−1. Quantum mechanical (QM) calculations on the newly obtained PES were used to provide the bound levels of the complex. Finally, integral and differential QM cross sections in Ar + N2 collisions were calculated at collision energy corresponding to the average temperature of the experiments and at room temperature. [Display omitted] •Neutron scattering experiments were performed in supercritical Ar-N2 mixtures.•Empirical potential structure refinement and classical molecular dynamics (MD) simulations were used to model the experimental data.•A new ab initio interaction potential energy surface was derived and was in good agreement with the classical MD model.•Values of the energy values of the bound rotational levels were calculated using the ab initio potential energy surface.•Integral and differential cross sections were obtained using quantum mechanical calculations.