Intrinsic-reaction-coordinate calculations
The potential energy profiles along intrinsic reaction coordinate (IRC) can be computed via damped velocity Verlet algorithm of Hratchian and Schlegel[1].
Experienced users can affect the performance of the dimer method by modifying the numerical values of the following parameters (the given example values are the default values):
- IRC_DIRECTION direction of the initial displacement (-1|1 – negative|positive)
- IRC_STOP = 20 the number of steps the energy must monotonously increase, used as a termination criterion for the DVV procedure (going from TS you expect to decrease energy till you reach a minimum (that’s the time to stop) and then energy increases again). In order to avoid a premature simulation termination (especially close to TS, i.e. at the very beginning of simulation), e.g., due to a numerical noise, DVVEHISTORY should always be greater than 1 (10-50 usually does the job)
- IRC_MINSTEP = 0.0250
- IRC_MAXSTEP = 3.0000
- IRC_VNORM0 = 0.0020
- IRC_DELTA0 = 0.0015