"quadrupole" corrections for non-neutral systems?

[Peng]

Hi Matt,

Thanks for the suggestion. I'm hoping to calculate the correction 
periodically
during the simulation. For my system, the excess charge will be fairly
localized, but I'm wondering why the correction will fail if this is not the
case. Thanks so much!

Best regards,

Peng

On Thursday, September 21, 2017 at 3:06:55 AM UTC-5, Matt W wrote:
>
> You might want to output the electron density on a 3D grid
>
>
> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/E_DENSITY_CUBE.html
>
> Probably you want to do this for the ideal and defect system, and subtract 
> the two densities (https://www.cp2k.org/tools:cubecruncher might be 
> useful).
>
> Hopefully this would give you a fairly localised density that you can then 
> calculate the dipole / quadrupole moments of. If it isn't localised, then 
> probably the correction schemes break down anyway ...
>
> Matt 
>
> On Saturday, September 9, 2017 at 1:25:56 PM UTC+8, Peng wrote:
>>
>> Hi all,
>>
>> I'm wondering if it's currently possible with CP2K to apply a correction 
>> for
>> non-neutral periodic system as in Eq. 14 of G. Makov & M. C. Payne, Phys 
>> Rev B
>> 51 4014 (1995), which involves determining the center of charge as well 
>> as an
>> integration: \int_cell dr^3 \rho(r) r^2. I assume the first part is just 
>> related
>> to the total system dipole calculated with respect to the origin of the
>> coordinate system (CP2K_INPUT / FORCE_EVAL / DFT / PRINT / MOMENTS / 
>> REFERENCE =
>> 0), but how should I go about computing the integral? If it's not directly
>> supported, can someone please give some quick pointers on where and how 
>> to hook
>> into the each MD step to implement this? Any suggestions would be really
>> helpful. Thank you very much!
>>
>> Best regards,
>>
>> Peng
>>
>
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