[QE-developers] A question concerning a QE development

[laurent pizzagalli]

Dear Paolo,

thanks for your help. I didn't think of the external file, which is 
probably the most flexible option. The ATOMIC_FORCES card seems a well 
defined container, and I am not sure it would be a good idea to 
introduce keywords in that place. Therefore the best way IMO would be to 
define a keyword in the &SYSTEM namelist, allowing for the activation of 
an external force field. The required parameters would then be read from 
an external file.

Best regards

Laurent

On 27/05/2021 22:04, Paolo Giannozzi wrote:
> 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
>>
>

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