Quantum-chemical study of the CH4⋯HCl complex

Abstract

An ab initio quantum-chemical study, largely at the MP2 level of theory, has been carried out on the CH₄⋯HCl complex, giving careful consideration to basis-set superposition effects and vibrational averaging. According to the calculations the complex has an effective C_3v equilibrium geometry, in agreement with the experimental findings. The computed intermolecular separation, stretching force constant, HCl librational amplitude and ³⁵Cl nuclear quadrupole coupling constant are in good agreement with experiment. A group-theoretical analysis, coupled with the ab initio results, confirms that the CH₄ moiety has the capacity to undergo internal rotation. The analysis of the interaction energy between CH₄ and HCl suggests that the dominant attractive term is dispersion.