[Wien] The new method of optimizing the internal parameter

[Laurence Marks]

The only difference is that with -min the run** code will switch from MSR1
to MSR1a, minimize, then switch back to MSR1 when the forces are small and
fully converge the density. Depending on what (old ?) version of run** you
are using it may not do this switching for you.

The later run** also has a way to automatically reduce RMT if touching
spheres are encountered, although I have never used these myself.

On Mon, Oct 15, 2018 at 9:46 AM karima Physique <physique.karima at gmail.com>
wrote:

> Dear Prof. Laurence Marks
> Thank you very much for your answer
> *For the case of my calculations, I want to optimize the internal
> parameters of an atom of a **chalcopyrite**, **usually I used MSR1a
> without -min (old WIEN2k versions) :*
> *runsp -fc 1*
> *save xxx*
> *i change MSR1 to MSR1a *
> *runsp -fc 0.5 -ec 0.00001 -cc 0.001 *
> *is this method better than -min option? or it's the opposite*
>
>
>
> Le lun. 15 oct. 2018 à 16:31, Laurence Marks <L-marks at northwestern.edu> a
> écrit :
>
>> There is in my opinion no "right" method. The question is what are you
>> trying to do?
>>
>> Case 1: A structure with fixed positions or a problem where you "don't
>> care" about minor forces, e.g. calculating a simple bulk structure. Then
>> just "runsp -cc 0.0001 -ec 0.0001" is fine. (I prefer to use -cc as well as
>> the default -ec).
>>
>> Case 2: A simple structure where there might be minor forces that you do
>> care about. Then something like "runsp -cc 0.0001 -ec 0.0001 -fc 1" first
>> and check the forces. Iff they are too large for you, then "save -f -d
>> PreMin ; runsp -cc 0.001 -ec 0.0001 -min" or similar.
>>
>> Case 3: A more complex structure where you know the positions are not
>> quite right. I suggest using something like
>> runsp -cc 0.01 -ec 0.1 -fc 4
>> save -f -d PreMin
>> runsp -cc 0.001 -ec 0.0001 -fc 1 -min
>>
>> This avoids converging too much at first when you know the result won't
>> be right until the internal minimization has been done. In addition, MSR1a
>> often works better when started from a partial minimization where the
>> density and pseudo-charges are somewhat converged. For a large problem add
>> "-noHinv", I have had problems with -min and -it in the past.
>>
>> On Mon, Oct 15, 2018 at 9:03 AM karima Physique <
>> physique.karima at gmail.com> wrote:
>>
>>> Dear Wien2k user;
>>>
>>> According to user guide, after a SCF cycle with runsp -fc 1 we continue
>>> with  run runsp -min
>>> I want to know which of these two methods is the correct one:
>>> 1)
>>> runsp -fc 1
>>> runsp -min
>>> runsp -min -fc 0.5 -ec 0.0001 -cc 0.001
>>>
>>> or
>>> 2)
>>> runsp -fc 1
>>> runsp -min -fc 0.5 -ec 0.0001 -cc 0.001
>>>
>>
>>
>> --
>> Professor Laurence Marks
>> "Research is to see what everybody else has seen, and to think what
>> nobody else has thought", Albert Szent-Gyorgi
>> www.numis.northwestern.edu ; Corrosion in 4D:
>> MURI4D.numis.northwestern.edu
>> Partner of the CFW 100% program for gender equity,
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>>
>

-- 
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody
else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu ; Corrosion in 4D: MURI4D.numis.northwestern.edu
Partner of the CFW 100% program for gender equity, www.cfw.org/100-percent
Co-Editor, Acta Cryst A
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