Hello
What value are you using for conv_thr in the electrons namelist ? You
should use a value which is rather lower than the default at least
something like 1.d-9. It this is the case the should be some warning
just after the forces summary at the end of each force computation.
I hope this helps
Pietro
On 9/12/19 3:33 AM, Gui Wei wrote:
Dear QE users,
When I optimized the structure of a heterostructure (containing about
130 atoms),it does converges as expected,and there is basically no
problem with the atomic structure.The convergence threshold I used was
*etot conv thr: 2.0D-4* *forc_conv_thr:2.0D-3*.By comparing with the
parameter design in the literature (similar model，usually using
software VASP),I think this convergence accuracy is relatively
rough,especially force.So I raised the threshold to *etot conv thr:
1.0D-4 * *forc_conv_thr:2.0D-3.*At this point I found that the
structure optimization could not converge.I extracted the data from
the output document and plotted Energy difference-Scf cycles curve and
Max force-Scf cycles curve.I found that scf cycles =5 satisfies the
convergence of the former rough convergence(both energy and
force).After that,two curves rise synchronously,this means that the
latter's fine convergence accuracy will never be achieved.
What I want to know is whether the atomic structure under the rough
precision can be counted as a stable structure.If so, how do I
understand the rise of the above two curves (this seems to be that the
structure is not stable, in my understanding, if it is a stable
structure, the two curves should continue to slowly decline,
eventually reaching an almost horizontal state).If not, what is the
solution?
Wei gui
School of Mechanical Engineering，Chongqing University, China
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