[CP2K-user] [CP2K:19290] Re: How to compute and output the dipole of the whole system during AIMD simulations?

[Matt Watkins]

The moments keyword gives the dipole moment of the whole system (which you 
seem to ask for). If your system if periodic you need to allow for that 
with the periodic keyword - dipole moments in a periodic system are only 
defined up to a point - consider drawing a box with two charges in it then 
shifting the box boundaries. There are many papers on this in the 
literature.

The localise keyword converts the density into a Wannier representation 
centred on atoms from the original distributed density. These wannier 
centres can then be used to recalculate the dipole of the whole system or 
by grouping the wannier centres that correspond to molecules (as defined in 
a similar way to a forcefield calculation) molecular dipoles can be 
calculated. See PL Silvestrelli, M Parrinello - Physical Review Letters, 
1999 - APS for instance.

Matt
 

On Wednesday, 27 September 2023 at 14:29:41 UTC+1 liu dongfei wrote:

> Recently, I have been trying to find commands in the reference manual and 
> cp2k group for calculating dipole of the simulation system.
> I find one previous related message posted two years ago.
> https://groups.google.com/g/cp2k/c/KPmGDOqhwMM/m/QdTYMNZhAgAJ
> In that post, Mr. Chen mentioned three commands for calculating dipole in 
> cp2k reference manual. They are as follows:
>
>    1. Total dipole: 
>    https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/LOCALIZE/PRINT/TOTAL_DIPOLE.html
>    2. Molecular dipole: 
>    https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/LOCALIZE/PRINT/MOLECULAR_DIPOLES.html
>    3. moments: 
>    https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/PRINT/MOMENTS.html
>    
> Mr. Chen said there exist differences between the results of Total dipole 
> and Molecular dipole. And the way of calculating Molecular dipole is also 
> unknown. 
>
> Mr. Chen's questions are also something that I want to know very much. 
> Looking forward to any guidance and help! 
>
> Regards,
> Dongfei
>

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