Dear all,
I appreciate this topic has been discussed a number of times in the forum, with
the answer that all components of all forces should satisfy the forc_conv_thr.
This leads me to my probably very simple query that likely stems from a
misunderstanding.
when I run a vc-relax calculation with e.g. a very tight forc_conv_thr=1.0D-5,
my calculation finishes 'successfully' with e.g.:
atom 1 type 3 force = 0.00000250 0.00000250 0.00000250
atom 2 type 3 force = 0.00000432 0.00000559 0.00000432
atom 3 type 3 force = 0.00000432 0.00000432 0.00000559
atom 4 type 3 force = 0.00000559 0.00000432 0.00000432
atom 5 type 2 force = -0.00000391 0.00000100 0.00000100
atom 6 type 2 force = 0.00000361 -0.00001336 -0.00001336
atom 7 type 2 force = 0.00000100 -0.00000391 0.00000100
atom 8 type 2 force = 0.00000100 0.00000100 -0.00000391
atom 9 type 2 force = -0.00001336 -0.00001336 0.00000361
atom 10 type 2 force = -0.00001336 0.00000361 -0.00001336
even if I put rather ridiculous thresholds of forc_conv_thr=1.0D-7 it makes no
real difference to the force components:
atom 1 type 3 force = -0.00000456 -0.00000456 -0.00000456
atom 2 type 3 force = 0.00000832 0.00001867 0.00000832
atom 3 type 3 force = 0.00000832 0.00000832 0.00001867
atom 4 type 3 force = 0.00001867 0.00000832 0.00000832
atom 5 type 2 force = -0.00000414 -0.00000409 -0.00000409
atom 6 type 2 force = -0.00000040 -0.00004042 -0.00004042
If I understand the output correctly, it appears as though some force
components have converged fine, though quite a few components have not reached
the threshold, and changing the threshold makes little difference. As we do a
lot of work on vibrational dynamics in dispersion bound crystals, tight forces
are usually quite important. We've recently moved into using QE and I'm trying
to get to grips with how to control the forces in QE optimisations but am
clearly missing something. Could anybody please point me in the right direction?
Many thanks in advance,
Adam
Adam Michalchuk
University of Birmingham UK
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