Band structure calculation with external periodic potential

[NGastaPooh]

Dear All,

I need to utilize the ability of CP2K to subject the electrons to an externally imposed electric 

field but am not sure as to exactly how this is implemented in the code. I would greatly appreciate 

it, if anyone could provide me with some details or direct me to the sub-routine that accounts for the external potential implementation.

I also have a separate question: what are the energy units in BAND_STRUCTURE routine output file? 

Thank you in advance.

Best regards,

Roman Dmitriev

[Matt W]

Hi,

there are, in principle, several ways of applying an electric field. The only way that makes proper sense for a periodic solid is the periodic efield
.  I would be (very) surprised if it works with k-points. The main methods are in qs_efield_berry.F. 

See 

 Stengel, Massimiliano; Spaldin, Nicola A.; Vanderbilt, David. 

 NATURE PHYSICS, 5 (4), 304-308 (2009). 

 Ab initio molecular dynamics in a finite homogeneous electric field

 Electric displacement as the fundamental variable in

 electronic-structure calculations.

 http://dx.doi.org/10.1038/NPHYS1185

and

Zhang, Chao, Jürg Hutter, and Michiel Sprik. "Computing the Kirkwood g-Factor by combining constant maxwell electric field and electric displacement simulations: application to the dielectric constant of liquid water." The journal of physical chemistry letters 7.14 (2016): 2696-2701.

There is also a non periodic version that might be easier to follow (efield_utils.F) and a general external potential that could be applied. Depends what you want to do.

Matt

[Roman Dmitriev]

Hello Matt,

Thank you very much for your answer. I want to periodically shift electronic charge density throughout a periodic solid to create a charge density "wave". The next step would be to observe the effect of such density change on a band structure of the solid. 

As far as I understood from your answer, the only way is to go with external potential. Does it sound right? If so, could you please direct me to the source file for it?

Thanks in advance.

Best regards,

Roman Dmitriev.

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[Matt W]

Look in qs_external_potential.F for the code.

It is quite flexible. You can supply a function in analytic form in this section. You should be able to set up a periodic external potential without any coding, I think.

Matt  

[Roman Dmitriev]

Thanks again. I’ve already looked through that section, it seems to be what I need. I’ll check the source file to make sure that I understand things correctly.

Appreciate your help.

Best regards,

Roman Dmitriev.