Intrinsic-reaction-coordinate calculations

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Revision as of 11:05, 7 December 2022 by Tbucko (talk | contribs)

The potential energy profiles along intrinsic reaction coordinate (IRC) can be computed via damped velocity Verlet algorithm of Hratchian and Schlegel[1].

  • IRC_DIRECTION direction of the initial displacement (-1|1 – negative|positive)
  • IRC_STOP = 20 the number of steps the energy must monotonously increase before the algorithm terminates. In order to avoid a premature terminations, especially close to transition states., e.g., due to a numerical noise, IRC_STOP should always be greater than 1.
  • IRC_DELTA0 = 0.0015 the desired error – the smaller value, the closer the computed trajectory follows the true IRC (but the more DFT steps is needed)
  • IRC_MINSTEP = 0.0250
  • IRC_MAXSTEP = 3.0000
  • IRC_VNORM0 = 0.0020


Mind: This method is presently available only for fixed cell shape (i.e., ISIF 2).
Mind: The calculation must be initialized from a very well relaxed transition state (EDIFFG-0.005 or less in absolute value)