[Pw_forum] Slab optimization with -24kbar stress!!!
smn at ims.uconn.edu
Fri Dec 5 17:06:07 CET 2014
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 correct?
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
somewhere in between.
I am not an expert on CeO, but could imagine that all of these cases may be
appropriate -- depending on what you
are after. The latter is for you and your advisor (I hope you got one?) to
figure out. Usually you have to take hint
from experiments, i.e., find out what sort of films and surfaces
experimentalists are dealing with, and then
decide how you can mimic this in your simulation.
Serge M. Nakhmanson
Dep-t of Materials Science & Engineering, and Institute of Materials Science
University of Connecticut
Storrs, CT 06269-3136
Phone: (860) 486-5252
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