DENSITY-FUNCTIONAL STUDIES OF THE N-CENTER-DOT-A-SIGMA CHARGE-TRANSFER COMPLEX BETWEEN SULFUR-DIOXIDE AND CHLORINE MONOFLUORIDE

The n.a sigma charge-transfer complex formed by sulfur dioxide and chl orine monofluoride has been studied with various approximate pure and hybrid density functional methods and the second-order Moller-Plesset (MP2) theory. The calculations demonstrate that one pure method and on e hybrid method, namely, the so-called BLYP and BHHLYP, respectively, lead to reasonably goad estimates of the experimentally measured rotat ional constants. However, the predicted BHHLYP intermolecular distance is found to be noticeably closer to the experimental value. Our best estimation for the intermolecular interaction energy is 1.93 kcal/mol. We have also been able to calculate the number and energies of the vi brational states supported by the intermolecular stretching mode. Only 11 such states have been found. The performance of the various approx imate density functionals and the MP2 theory is compared and discussed . Finally, we comment on the analysis of the natural bond orbitals, wh ich has been found to be very valuable to shed light on the nature of weak intermolecular interactions.