Quantum-Chemical Study Of The Ch4...Hcl Complex

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 C3v equilibrium geometry, in agreement with the experimental findings. The computed intermolecular separation, stretching force constant, HCI librational amplitude and Cl-35 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 HCI suggests that the dominant attractive term is dispersion.