[QE-developers] A question concerning a QE development

[Paolo Giannozzi]

Dear Laurent

the proliferation of input variables in QE is an old and known problem. 
I am not sure what the best solution should be, though. One possibility 
I would consider is to read the needed variables from a separate file.
If I remember correctly this is what the "Environ" library does.
Another one is to extend the existing ATOMIC_FORCES card, that currently 
supports only a list of forces, to cover your case as well.

Paolo

On 27/05/2021 10:00, Laurent Pizzagalli wrote:
> Dear Dr. Giannozzi,
> 
> 
> I write to you concerning the implementation of an external force field 
> in quantum espresso. The motivation is the investigation of the 
> mechanical properties of nanoparticles, especially in the plastic 
> regime, obtained by uniaxial compression. The implementation is not 
> complicated, since you (the developers) had already planned this 
> potentiality in the file 'plugin_ext_forces.f90'.
> Actually, i already made the implementation in cp.x, but in a quick way, 
> in a local copy of the code. Since it is successful, I would like to do 
> it properly, merging it with the development version using git. I got 
> almost all the information I need in the developer manual. But I still 
> have one question, concerning the general organization of the input. 
> Right now, I implemented only one kind of force field, fully repulsive. 
> It allows for compressing the nanoparticle between two planes. Six 
> keywords are needed, one for the activation of the force field, four to 
> define the position of the planes and the increment for their 
> displacements at each timestep, and a last one to define the strength of 
> the repulsion. My question is: what would be the best way to organize 
> these keywords? Originally, I put all of these into the &IONS namelist. 
> Another option would be in the &SYSTEM namelist. And finally, maybe it 
> would be better to create a specific NAMELIST to include these keywords 
> (something like &EXTFF)? I also plan to implement another force field 
> (including an attractive interaction), which would require other 
> keywords. So the creation of a specific NAMELIST seems the best option 
> in my opinion. But I would like to have yours before proceeding.
> 
> Best regards
> 
> Laurent
> 

-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222