mirror of https://gitlab.com/QEF/q-e.git
35 lines
1.6 KiB
Plaintext
35 lines
1.6 KiB
Plaintext
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This example shows how to use neb.x to calculate the minimum energy path (MEP)
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of a simple activated reaction i.e. the collinear proton transfer reaction :
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H2 + H <==> H + H2
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The MEP is obtained by means of the Climbing-Image Nudged Elastic Band (CI-NEB)
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method and two different climbing image algorithms are used ("auto" and
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"manual").
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(for the meaning of the cited input variables see the Doc/INPUT_NEB* files)
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The symmetric reaction path H2 + H <==> H + H2 is calculated in three
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different ways.
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1) The path connecting the initial and the final configurations is discretized
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with an odd number of images (7) so that the standard CI_scheme ("auto")
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will give rise to a symmetric MEP (3 images on the left of the saddle point
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and 3 images on the right). Note that in this system the use of the climbing
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image is not necessary. Indeed using CI_scheme = "no-CI" the result is the
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same.
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2) The path connecting the initial and the final configurations is discretized
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with an even number of images (8) and no climbing image is used. The
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resulting path is symmetric, but no image is at the saddle point.
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3) The path connecting the initial and the final configurations is again
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discretized with an even number of images (8), but the "manual" CI_scheme
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is used so that the resulting path is asymmetric. The image 5 now is at the
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saddle point.
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Given the low accuracy of these calculations (plane waves cut-off and
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thresholds) and the small box employed, these results should not be
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compared with experiments or with other "ab initio" calculations.
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