force of fixed ion will not go to value of EDIFFG?

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mariesto · #1 Post by **mariesto** » Sat Mar 21, 2009 12:06 pm

Dear All,

I did relaxation with EDIFFG = = -0.01 . . I thoght that fixed condition means the ions does not move that resultant force should be zero or at least close to value of EDIFFG.
But in OUTCAR I found that force of fixed ions did not go to value of 0.001. The forces are remain big. Is it normal?

thank you in advance.

#2 Post by **admin** » Thu Mar 26, 2009 8:00 am

if you use selective dynamics and fix some atoms, the force on these atoms is calculated, but the ions are not relaxed. Also, the forces on these atoms are neglected when vasp checks whether the ionic relaxation convergence criteruium is matched.

mariesto · #3 Post by **mariesto** » Sat Mar 28, 2009 2:58 am

thank a lot for your explanation. But, sorry I need confirmation and more clarity. Would you please answer my two questions

I fixed some atoms. forces on these atoms remains big while forces of relaxed atoms have reached very small value (below value of EDIFFG).
1) Has my system reached its minimum in that condition?

2) what values actually displayed as force of fixed ions in OUTCAR?

best regards