Z. Konkoli et al., DIABATIC ORDERING OF VIBRATIONAL NORMAL-MODES IN REACTION VALLEY STUDIES, Journal of computational chemistry, 18(10), 1997, pp. 1282-1294
Diabatic ordering of the normal model of a reaction complex along the
reaction path has several advantages with regard to adiabatic ordering
. The method is based on rotations of the vibrational normal modes at
one Feint, s, of the reaction path to maximize overlap with the vibrat
ional modes at a neighboring Feint. Global rotations precede the rotat
ions of degenerate modes so that changes in the direction of the react
ion path and changes in the force constant matrix, which represent the
two major effects for changes in mode ordering, can be separated. Ove
rlap criteria identify resolved and unresolved avoided crossings of no
rmal modes of the same symmetry. Diabatic mode ordering (DMO) can be u
sed to resolve the latter by reducing the step size, thus guaranteeing
correct ordering of normal modes in dependence of s. DMO is generally
applicable to properties of the reaction complex that depend on s suc
h as normal mode frequencies, orbital energies, the energy of excited
states, etc. Additional applications are possible using a generalized
reaction path vector, which may describe the change in atom masses, ge
ometrical parameters, and/or the force constant matrix. In this way, t
he vibrational spectra of isotopomers can be investigated or the vibra
tional frequencies of different molecules correlated. (C) 1997 by John
Wiley & Sons, Inc.