Dimers involving methane: Strength, range, and nature of the intermolecular interaction and their thermodynamic stability in gas-phase

This work focuses on an accurate theoretical characterization of the strength, range, and nature of the weak intermolecular interaction that controls the formation of CH${}_4$ CH${}_4$, CH${}_4$ N${}_2$, and CH${}_4$ Ar gaseous dimers. It also provides a reliable valuation of the thermodynamic stability of such three adducts and of their relative distribution of populated intermolecular vibrational levels. The formation of these dimers is driven by the negative components of enthalpy and entropy, indicating that these complexes form nonspontaneously through gas-phase collisions. The results also suggest that the main interaction contribution controlling the stability of these adducts is the dispersion attraction. Furthermore, the formation of the CH${}_4$ CH${}_4$ complex, driven by the stronger interaction, exhibits the least positive free energy variation over a wide range of considered temperatures. The obtained information is of relevance since it opens up a range of applications in several areas, including chemistry, materials science, and astrophysics.