[Wien] Huge Forces

[stargmoon]

Dear Kevin and Laurence,
 
Thanks a lot for your kind reply. Especially, Laurence's explanation make me feel comfortable with my calculations.
 
Thanks again.
 
Best,
 
Stargmoon

Jorissen Kevin <Kevin.Jorissen at ua.ac.be> wrote:
Sorry for last night's e-mail full of rubbish.
Thanks, Laurence, for correcting me.



Kevin Jorissen

EMAT - Electron Microscopy for Materials Science (http://webhost.ua.ac.be/emat/)
Dept. of Physics

UA - Universiteit Antwerpen
Groenenborgerlaan 171
B-2020 Antwerpen
Belgium

tel +32 3 2653249
fax + 32 3 2653257
e-mail kevin.jorissen at ua.ac.be


________________________________

Van: wien-admin at zeus.theochem.tuwien.ac.at namens L. D. Marks
Verzonden: za 13-11-2004 0:34
Aan: wien at zeus.theochem.tuwien.ac.at
Onderwerp: RE: [Wien] Huge Forces



Sorry Kevin, but I don't think your explanation is quite right:

1) The -fc option calculates the forces at the end of a scf cycle, setting
"FOR" in case.in2. The use of -I is recommended since it will reset
case.in2 to the default "TOT" which is often much faster (lapw2 can be
rather slow for forces, comparable to lapw1)

2) At the start of an iteration after you have moved the atoms, the
electronic configuration is in a strange state. The forces, which are
often very large, don't have any physical meaning; you can only say
something about the forces with a converged calculation.

What you are seeing in your calculation sounds OK to me.

On Sat, 13 Nov 2004, Jorissen Kevin wrote:

>
> Dear WIEN2k users,
>
> I started to optimize the internal parameters from a substituted supercell system, the output forces after the first interation is very huge, more than 1000mRy/au. It converged to 1.76mRy/a.u after the mini_lapw stoped.
>
> The problem is that the force is even bigger than that of my initial structure when I use the optimized structure to do a new interation. But the output force for the last iteration for the optimized structure is okay. I am wondering are there something wrong with my calculations?
>
> Look forward to your reply.
>
> Stargmoon
>
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-----------------------------------------------
Laurence Marks
Department of Materials Science and Engineering
MSE Rm 2036 Cook Hall
2225 N Campus Drive
Northwestern University
Evanston, IL 60201, USA
Tel: (847) 491-3996 Fax: (847) 491-7820
mailto:L-marks at northwestern.edu
http://www.numis.northwestern.edu
-----------------------------------------------

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