[Pw_forum] Slab optimization with -24kbar stress!!!
davidfoster751 at yahoo.com
Fri Dec 5 17:38:14 CET 2014
Thank you for your help. I think the best judge for this issue is experimental data for adsorption process, as you noted.
Thank you Nicola, Cyrille, and Serge for your helps.
Ph.D. Student of Chemistry
On Fri, 12/5/14, Serge Nakhmanson <smn at ims.uconn.edu> wrote:
Subject: Re: [Pw_forum] Slab optimization with -24kbar stress!!!
To: "PWSCF Forum" <pw_forum at pwscf.org>
Date: Friday, December 5, 2014, 7:36 PM
On 12/5/14 10:36 AM,
David Foster wrote:
> If I do according
to the published works, I get large stress, as it was
discussed in previous long discussion.
If I do according to Nicola's advice, the stress
eventually reduces, but the bottom layers positions will not
be the bulk ones.
> Which one is
I do not think you are asking
the right question here.
IMO, the appropriate question is: what elastic
condition on my system do I want
If you want to do
a surface that is rigidly clamped to the bulk, you will get
(correctly!) non-zero residual stress.
BTW, a 24 kBar stress is not large, unless you
got a very soft system like a
If you want to do a surface that is completely
relaxed, do a vc-relax on your
slab and get
rid of the stress completely.
Finally, you can also do a partially relaxed
surface and get a stress that is
I am not an
expert on CeO, but could imagine that all of these cases may
appropriate -- depending on what you
are after. The latter is for you and your
advisor (I hope you got one?) to
out. Usually you have to take hint
experiments, i.e., find out what sort of films and surfaces
experimentalists are dealing with, and
decide how you can mimic this in your
Serge M. Nakhmanson
Dep-t of Materials Science & Engineering,
and Institute of Materials Science
University of Connecticut
Storrs, CT 06269-3136
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