ON THE INTERPOLATION OF THE FREQUENCIES OF VIBRATIONAL-MODES IN VARIATIONAL TRANSITION-STATE CALCULATIONS - AN ADIABATIC OR DIABATIC SCHEME

The convenience of a diabatic or an adiabatic interpolation of frequen cies in variational transition state calculations involving interpolat ion methodologies is discussed. The gas phase proton transfer between butanone and a hydroxide anion has been used to illustrate the theoret ical discussion. For example, it has been shown that if vibrational no rmal mode crossings exist the simple adiabatic interpolation can produ ce incorrect entropy contributions and, as a consequence, a spurious d isplacement of the generalized transition state.