|FORWARD||The IRC is calculated in the forward direction of the transition state eigenvector of the Hessian.|
|REVERSE||The IRC is calculated in the reverse direction of the transition state eigenvector of the Hessian.|
|MASS||The IRC is calculated in mass-weighted coordinates.|
|NOMASS||The IRC is calculated without mass-weighting coordinates.|
|RESTART||The IRC calculation is restarted. Previous steps are read from the file deMon.trj.|
|EXTEND||An already-calculated IRC branch is extended.|
|MAX=Integer||Maximum number of IRC steps. Default is 50.|
|STEP=Real||Maximum radius size for IRC optimization. Default is 0.1 (amu) Å.|
|TOL=Real||Convergence criterion for IRC end-point gradients. Default is atomic units.|
|EVIB=Real||Energy threshold for transition state kick-off. Default is Hartree.|
|READ=Integer||Number of IRC pivot points for which coordinates are read from the file deMon.trj.|
IRC REVERSE EXTEND
As a result, the trajectory and molden files deMon.trj and deMon.mol
contain both branch-
es and, thus, the full reaction coordinate. Coordinates of a specified pivot point along the IRC path can be loaded with the READ option of the IRC keyword. In this way, properties or molecular fields can be calculated or plotted along the IRC path.
By default, the IRC path is calculated in mass-weighted coordinates. The mass-weighting is disabled with the option NOMASS. With the MAX option of the IRC keyword, the maximum number of IRC steps can be specified. The RESTART option permits the restart of an IRC calculation, e.g. if not enough IRC steps were requested in a previous run. The IRC calculation restarts with the last successfully calculated pivot point. As always, the restart input can be found in the deMon.new file. For the IRC restart, the file deMon.mem, must be renamed to deMon.rst, and the file deMon.trj must also be available. The TOL option specifies the convergence criterion for the RMS gradient at the IRC path end points. The convergence of the constrained optimizations in each IRC step can be modified with the OPTIMIZATION keyword. Cartesian constants can be used in an IRC calculation. With the EVIB option, the energy decrease for the transition state kick-off (that is, the energy decrement to initiate the search) along the transition state eigenvector is specified. This energy value is given in Hartree.