In the pursuit of small "red shift" of C-H stretching vibrational frequency of C-H...pi interactions for benzene dimer: How to amend MP2 calculations to reproduce the experimental results.

For the bent T-shaped benzene dimer, the vibrational frequencies at the MP2/aug-cc-pVDZ level with counterpoise correction reproduce experimental results of the small "red shifts" of C-H stretching, while those without counterpoise correction yield considerable "blue shift." Counterpoise correction also affects the C-H bond distances of C-H...pi interactions as well as intermoiety distances.