Intrinsic-reaction-coordinate calculations: Difference between revisions
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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 | 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 damped velocity Verlet algorithm. The damping is realized via rescaling the velocity vectorto a constant value (<math>v_0</math>) after each propagation step. | ||
*{{TAG|IRC_DIRECTION }} direction of the initial displacement (-1|1 – negative|positive) | *{{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. | *{{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. | ||
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*{{TAG|IRC_MINSTEP}} = 0.0250 | *{{TAG|IRC_MINSTEP}} = 0.0250 | ||
*{{TAG|IRC_MAXSTEP}} = 3.0000 | *{{TAG|IRC_MAXSTEP}} = 3.0000 | ||
*{{TAG|IRC_VNORM0}} = 0.0020 | *{{TAG|IRC_VNORM0}} = 0.0020 the value of <math>v_0</math> in {\AA}/fs | ||
Revision as of 11:15, 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 damped velocity Verlet algorithm. The damping is realized via rescaling the velocity vectorto a constant value () after each propagation step.
- 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 the value of in {\AA}/fs
| 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). |