Intrinsic-reaction-coordinate calculations: Difference between revisions

Revision as of 11:11, 7 December 2022

The potential energy profiles along intrinsic reaction coordinate (IRC) can be computed via d method of Hratchian and Schlegel^[1]. The algorithm starts from transition state and propagates the system via velocity Verlet algorithm, whereby the of the velocity vector is set to a constant value of : $v_0$

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) simulations.

Mind: The calculation must be initialized from a very well relaxed transition state (EDIFFG = -0.005 or less in absolute value).

↑ H. P. Hratchian and H. B. Schlegel, J. Phys. Chem. A 106, 165 (2002).

[1] H. P. Hratchian and H. B. Schlegel, J. Phys. Chem. A 106, 165 (2002).

[1]

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-The potential energy profiles along intrinsic reaction coordinate (IRC) can be computed via damped velocity Verlet algorithm of Hratchian and Schlegel<ref>[https://pubs.acs.org/doi/abs/10.1021/jp012125b H. P. Hratchian and H. B. Schlegel, J. Phys. Chem. A 106, 165 (2002).] </ref>.
+The potential energy profiles along intrinsic reaction coordinate (IRC) can be computed via d method of Hratchian and Schlegel<ref>[https://pubs.acs.org/doi/abs/10.1021/jp012125b H. P. Hratchian and H. B. Schlegel, J. Phys. Chem. A 106, 165 (2002).] </ref>. The algorithm starts from transition state and propagates the system via velocity Verlet algorithm, whereby the of the velocity vector is set to a constant value of :<math>v_0</math>
 *{{TAG|IRC_DIRECTION }} direction of the initial displacement (-1|1 – negative|positive)
 *{{TAG|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,  {{TAG|IRC_STOP}} should always be greater than 1.