[Pw_forum] NEB Image Continuity

[Paolo Giannozzi]

A simple check that your path is what you expect and not something else is
provided by the "path length", a quantity that is reprinted on output. All
visualizers occasionally show atoms that seem to "jump" from one side to
the other of the cell.

P.

On Sat, Jan 23, 2016 at 3:44 PM, Vic Bermudez <c.h.bermudez at cox.net> wrote:

> Hello,
>
>         I have a question about the issue of image continuity in NEB
> calculations.
> The NEB users' guide (vers. 5.0) contains the following cautionary note:
>
>         "Remember that Quantum ESPRESSO assumes continuity between the
> first and
> the last image at the initial condition. In other words, periodic images
> are
> NOT used; you may have to manually translate an atom by one or more unit
> cell base vectors in order to have a meaningful initial path."
>
> I've checked my reaction path by viewing the .axsf output file in XCrysDen
> with the setting Display -> Unit of Repetition -> Translational Asymmetric
> Unit. I don't see any problem with atoms jumping by one unit-cell vector
> between images or with atoms getting too close. I do, however, see a few
> atoms jumping when I use Display -> Unit of Repetition -> Unit Cell.
>
>         My understanding is that Quantum Espresso works with the
> Asymmetric Unit
> (or primitive unit cell), so my NEB path appears to satisfy the cautionary
> note. Is that correct ? Unfortunately, for technical reasons, I don't have
> access to vers. 5.1, so I can't simply use the minimum_image option that's
> available in vers. 5.1.
>
>         Thank you in advance for your help and advice.
>
> Best Wishes,
> Vic Bermudez
>
> Victor M. Bermudez
> E-mail: bermudez at alum.mit.edu
>
>
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-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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