Dear Prof. Marks, Thank you for your explanations Sir. Comments are very informative.
with regards, On Wed, 6 Oct 2021 at 18:30, Laurence Marks <laurence.ma...@gmail.com> wrote: > Some mixer and optimization comments, to clarify. > > 99.999% of cases where there are convergence problems are due to: > > 1) Inappropriate physics. A bad model does not have to have a fixed-point > solution, that is there may be no converged solution. (Nothing says there > has to be.) > > 2) Inappropriate numerics. For instance, a functional that jumps around > very noisily may not be smooth. I know this can happen for 4f electrons > using -eece. > > 3) Discontinuity at the solution. There is such a discontinuity > (electronic phase transition) for systems such as isolated Fe atoms without > spin, T=0. > > 4) User error. I recently ran a case with 16 symmetry elements which only > should have had 8. While it came close, it would not converge. > > Sometimes the pseudo-forces are quite bad with large density residues, so > MSR1a can be slow. There can also be issues if the electron-phonon coupling > is large. > > PORT is sometimes better, particularly with repetitive calculations such > as lattice parameter optimizations. However, it is very sensitive to > inconsistent forces and energies. > > In my opinion NEWT & NEWT1 should be removed. My opinion. > > Always look first at how the model is setup. > > -- > Professor Laurence Marks > Department of Materials Science and Engineering > Northwestern University > www.numis.northwestern.edu > "Research is to see what everybody else has seen, and to think what > nobody else has thought" Albert Szent-Györgyi > _______________________________________________ > Wien mailing list > Wien@zeus.theochem.tuwien.ac.at > http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien > SEARCH the MAILING-LIST at: > http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html > -- Dr. Shamik Chakrabarti Research Fellow Department of Physics Indian Institute of Technology Patna Bihta-801103 Patna Bihar, India
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