Gaussian 03 Online Manual
Performs an IRCMax calculation using the methods of Petersson and coworkers [168,169,170,171,172,173,174,175,176]. Taking a transition structure as its input, this calculation type finds the maximum energy along a specified reaction path.
You should specify alternative isotopes for IRCMax jobs using the standard method.
IRCMax requires two model chemistries as its options, separated by a colon: IRCMax(model2:model1). Here is an example route section:
This calculation will find the point on the HF/6-31G(d,p) reaction path where the B3LYP/6-31G(d,p) energy is at its maximum.
This job will start from the HF/3-21G* TS and search along the HF/3-21G* IRC with a stepsize of 0.1 amu1/2 bohr until the maximum of the MP2/6-31G(d) energy (including the HF/3-21G* ZPE scaled by 0.91671) is bracketed. The position along the HF/3-21G* IRC for this MP2/6-31G(d) TS will then be optimized. The output includes all quantities required for the calculation of reaction rates using the ZC-VTST version of absolute rate theory: TS moments of inertia, all real vibrational frequencies (HF/3-21G*), the imaginary frequency for tunneling (fit to MP2/6-31G(d) + ZPE), and the total MP2/6-31G(d) + ZPE energy of the TS.
PATH SELECTION OPTIONS
COORDINATE SYSTEM SELECTION OPTIONS
forces (lines of format 6F12.8)
Force constants (lines of
The force constants are in lower triangular form: ((F(J,I),J=1,I),I=1,NAt3), where NAt3 is the number of Cartesian coordinates. If both FCCards and ReadIsotopes are specified, the masses of the atoms are input before the energy, Cartesian gradients and the Cartesian force constants.
Analytic gradients are required for the IRC portion of the calculation (model1 above). Any non-compound energy method and basis set may be used for model2.