Symmetry of the electronic state.   It does not affect the rate constant and thermodynamic calculation.   It is rather important to give gElec or eStates shown below, which are directly used for calculations.

default: determined from the output.

  Degeneracy of the electronic state including both the electronic spin degeneracy and the electronic angular momentum degeneracy.   For example for OH radical, one may need to specify to account for the ²Π electronic state (spin multiplicity = 2 and anglular momentum multiplicity = 2);

gElec 4

or specify the fine structures by eStates (see below).

default: determined from the output (note-1).

  Fine elctronic states specification. If this key is specified, the gElec key is completely ignored. nEstates is the number of electronic states, followed by nEstates pairs of (g energy) where g and energy are the degeneracy and the energy (in cm^–1 unit) of each state. Below is an example for the OH radical with ²Π_3/2 and ²Π_1/2 spin-orbit states.

eStates 2  2 -69.6  2 69.6

  Point group of the molecule.   It does not affect the rate constant and thermodynamic calculation.   It is rather important to give rotSymNbr and numIsomers shown below, which are directly used for calculations.

default: determined from the output.

  Rotational symmetry number.   For example for an H₂O molecule calculated with slightly asymmetric initial structure, one may need to specify to correct for the symmetry number as;

rotSymNbr 2

default: determined from the output (note-2).

  Number of isomers.   For example for a propene (C₃H₆) moleclule calculated with slightly assymmetric initial structure, one may need to specify to correct for the number of isomers as;

numIsomers 1

default: determined from the output (note-3).

  Isomeric species specifications. If this key is specified, the numIsomers key is ignored. nIsomSts is the number of isomeric species, followed by nIsomSts pairs of (n energy) where n and energy are the number of occurrence and the energy (in cm^–1 unit) of each isomeric species.   For example for butane (C₄H₁₀) with lowest C_2h (anti) conformer and two enantiomers of C₂ (gauche) form, one may need to specify;

isomStates 2  1 0  2 247

  A flag indicates the transition state. The value flag must be either of 'true' or 'false'.

default: determined from the output (note-4).

  Energy (in hartree unit) for rate constant calculation, and should correspond to the internal energy at 0 K. Since only the differences (between reactants and transition states, etc.) are significant, the energy can be defined from any zero point, which, however, should be common for all relevant molecules or atoms.

  This key (without any value followed) tell the program to use SCF level energy corrected for ZPE for rate constant calculations.

  Change the vibrational-frequency scaling factor to factor.

  This key tells the program to use, factor, for the scaling of vibrational frequencies in the zero-point energy calculation.   This affects the results when used with useSCFenergy+ZPE and/or setIntRotor.

  Definition of a intramolecular rotor. idVib is the index of the vibrational mode which is treated as a hindered internal rotor. If this index is set to 0 or negative value, gpop3tst automatically detects the most similar vibrational mode (note-5). nSym is the symmetry number of the internal rotation. moi1 and moi2 inputs specifies the intramolecular rotation and the format for these are the same as that in gpop6irt program. V0 is the height of the hindrance potential. if a positive V0 input is found, the value is used for calculation. If V0 is zero, it is treated as a free rotor. If V0 is negative, V0 is calculated from the eq. (2) below. comment is an optional comment field. The vibrational frequency is scaled by scaleFactZPE for the quantum mechanical correction and for the estimation of V0, in order to keep the consistency of zero-point energy.

note-1 (gElec)

Since the Gaussian often fails to determine the degenerated electronic states of highly symmetric molecules, the angular momentum degeneracy must be carefully considered by the user.

note-2 (rotSymNbr)

The rotational symmetry number is determined by the point group identified by the Gaussian. Note that the point group identification by Gaussian is done from the initial geometry specification, and the only slightly asymetric input results in the lower symmetry and thus, the incorrectly small symmetry number.

note-3 (numIsomers)

Only the number of the optical isomers, which is easily determined by the molecular symmetry, is set as the number of isomers by default. This default is not appropriate for hydrocarbon molecules with many rotational conformers. Usually, as far as it is possible to guess the energy of rotational conformers, the use of isomStates key is recommended instead of numIsomers.

note-4 (isTS)

The default is set 'true' if at least one imaginary vibrational frequency was found. This may not be correct for very loose transition states for variational calculations.

note-5 (setIntRotor)

This automatic detection is not always safe. If the corresponding vibrational motion is fairly localized, the result of autodetection is satisfactory, but if it couples strongly with other vibrational mode(s), the results may be inappropriate. See the manual of gpop6mrt for further discussion on this problem.