[Pw_forum] reusing converged density

[Stefano Baroni]

Thank you, Luke. the best way to proceed would probably be to first see what some of the "core developers" think.
Stefano de Gironcoli, Paolo Giannozzi, Layla Samos, Andrea Dal Corso, any ideas?
Once the eview is ready, it should be enough to submit it to Layla (Layla Martin Samos Colomer <lmartinsamos at gmail.com>) or Paolo (Paolo Giannozzi <paolo.giannozzi at uniud.it>)
Good luck and thanks for your interest and willingness to help
Stefano B

On Mar 1, 2010, at 3:52 PM, Luke Shulenburger wrote:

> Dear Stefano,
> 
> Thanks for the quick reply.  I think it probably best to stick with a solution inside the code.  It sounds like everything is already there and my job will more akin to plumbing than algorithm testing and validation.  I'll take a look at it soon.  What is the proper way to submit code for review once I get that far?
> 
> Luke
> Geophysical Laboratory
> Carnegie Institution of Washington
> (lshulenburger at ciw.edu)
> 
> 
> On Sun, Feb 28, 2010 at 4:17 AM, Stefano Baroni <baroni at sissa.it> wrote:
> Dear Luke:
> 
> I am no longer familiar with the guts of the code, but I think this would require some coding. The problem is, the PW basis set (and the related FFT grids) slightly depends on the strain state. In variable-cell MD, this dependence is eliminated by using a "hard" cutoff that defines the PW basis set and a "smooth" one that implicitly, but continuously, eliminates some of the PWs according to the strain state. I can see two strategies that you may want to try. 
> 
> The first would probably require you to put your hands into PW: you simply have to make the "soft" cutoff option available to static scf calculations. I believe this should be rather easy, and I will ask some of the people who know the code well to assist you if you want to try.
> 
> Second option. Do Fourier interpolation. Take the charge density / wavefunctions calculated and stored with one FFT grid and use a simple stand-alone program to calculate the fourier coefficients with respect to a different grid. Writing this simple code would not require any knowledge of the PW guts. If you want to give it a try, I can give you a few hints.
> 
> If you decide to try either one of the above two approaches, I beileve the QE developers' team would be more than glald to help and to include your contribution in a future distribution of QE.
> 
> Cheers
> Stefano B
> 
> On Feb 28, 2010, at 3:33 AM, Luke Shulenburger wrote:
> 
>> Hello,
>> 
>> I would like to calculate the ground state of a system with several different strains.  As the calculations are somewhat hard to converge, I was hoping that I could re-use the density and wavefunctions from one of the calculations as starting points of the others.  I know that the code does this under the hood when the geometry is changed in MD or geometry optimizations, but I cannot seem to get it to work for separate static scf calculations.   Is this feature available?
>> 
>> Luke Shulenburger
>> Geophysical Laboratory
>> Carnegie Institution of Washington
>> (lshulenburger at ciw.edu)
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> 
> ---
> Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
> http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)
> 
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale de la pensée - Jean Piaget

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html







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