[Wien] Huge Forces

[Jorissen Kevin]

Dear Stargmoon,
 
don't ask me how exactly wien calculates forces, but it takes some effort from your pc.  For that reason, the forces are only calculated correctly when you give the -I option to run_lapw.  Without this option, only part of the force is calculated (some terms are omitted).  Especially when you have converged the correct force to almost zero, the next run in a 'normal' run_lapw (where you don't have the -I to save a little time) will show bigger forces.
1000 mRY seems pretty large though, I've never had it that ugly.  Try doing run -I -fc 5.0 and see whether or not it gets smaller.
 
I wonder : how much speed is gained by not calculating the forces correctly?  If it is not much, we could 'invert' the default behaviour : it would make results less confusing for normal users, and advanced users could still gain the performance increase by giving an 'inverted -I' option.
 
good luck,
 
 
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 stargmoon
Verzonden: vr 12-11-2004 18:17
Aan: wien at zeus.theochem.tuwien.ac.at
Onderwerp: [Wien] Huge Forces


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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