TRANSITION-STATE LOCALIZATION BY A DENSITY-FUNCTIONAL METHOD - APPLICATIONS TO ISOMERIZATION AND SYMMETRY-FORBIDDEN REACTIONS

A new transition state algorithm incorporated into the density functio nal code deMon, has been used to study the trans --> cis-hydroxymethyl ene and trans-hydroxymethylene --> formaldehyde isomerization processe s and to localize the transition state for the decomposition of 1,3-di azacyclobutane to methyleneimine. Calculations have been performed usi ng both local (LSD) and nonlocal spin density (NLSD) gradient-correcte d approximations. Two different basis sets of small and large size hav e been used for the study in order to analyze the effect of the basis set dimension other than that of the nonlocal corrections on the activ ation energy barrier value. The results seem to confirm that density f unctional methods can be considered practical and reliable tools for t he localization of transition states.