[Wien] Charge convergence necessity

[Luis Ogando]

Dear Prof. Marks,

   Thank you very much for your answer !!
   All the best,
                        Luis

2015-07-15 21:26 GMT-03:00 Laurence Marks <L-marks at northwestern.edu>:

> I don't think I can give a complete answer, but I will make one point. It
> can easily happen that the energy convergence appears to be OK, but the
> charge convergence is not. The reason is that the energy convergence is
> measured as a change in energy over the last few iterations, whereas the
> charge convergence is based upon the difference of the initial and final
> densities in the current cycle. If, for whatever reason, the mixer is only
> taking very small steps the energy can appear to have converged, but in
> reality the true self-consistent solution (fixed point) has not been
> reached.
>
> Hence I almost always add something like -cc 0.001 as a minimum level. If
> I really want to be certain about the fixed point I might decrease this by
> a factor of 4-10, never more than this.
>
> N.B., for a preconvergence before switching to MSR1a -cc 0.05 is often
> good enough.
>
>
> On Wed, Jul 15, 2015 at 7:08 PM, Luis Ogando <lcodacal at gmail.com> wrote:
>
>>   Dear Wien2k community,
>>
>>     I would like to know in which situations the charge convergence is
>> really necessary.
>>     All the best,
>>                   Luis
>>
>>
>
>
> --
> Professor Laurence Marks
> Department of Materials Science and Engineering
> Northwestern University
> www.numis.northwestern.edu
> Corrosion in 4D: MURI4D.numis.northwestern.edu
> Co-Editor, Acta Cryst A
> "Research is to see what everybody else has seen, and to think what nobody
> else has thought"
> Albert Szent-Gyorgi
>
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