Vi. Tyulin et al., Improvement of the standard method for solving the problem of internal rotation in molecules with symmetrical tops, RUSS CHEM B, 48(2), 1999, pp. 239-244
Drawbacks of the standard method for solving the problem of internal rotati
on (IR) in molecules with symmetrical tops were examined. The drawbacks can
be eliminated by taking into account the higher harmonics of the IR potent
ials. A new calculation procedure based on the approximation of the lower p
ortion of the potential curve by the equation V(phi) = 1/2 V-n*(1 - cos n p
hi), which describes adequately the arrangement of the torsion levels, was
proposed. The successful implementation of the proposed procedure showed th
at the procedures used currently are incorrect as well as the Herschbach pr
ocedure, which includes a systematic error at each iteration step.