Dipole Moment with Berry Phase method

Pierre-André Cazade

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Jul 6, 2020, 6:19:24 AM7/6/20

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Dear CP2K users,

When using. a classical forcefield, is the dipole moment computed by FIST with the Berry Phase method the same thing as what is commonly called the Berry Phase? Furthermore, when using the polarizable forcefield, are the induced dipoles involved in the calculation of the Berry Phase dipole moment?

Regards,

Pierre

Ant Stone

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Jul 14, 2020, 9:22:32 AM7/14/20

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Dear Pierre:

I am a newbie, so I hope for your sake that someone more experienced responds to your question. However, I thought you might be interested to know that I have been having the same problem for months now with understanding how the dipole moment is calculated in CP2K. I don't think there is anyone around who knows about this anymore because I asked several questions myself some months ago and have not had any luck with responses. I suspect that whoever implemented dipole moment calculation in CP2K may have left the group. Unfortunately, I don't know of any other resources that might help us.

I'm running ab initio simulations and do not want to use Berry Phase. I didn't realize I was using it until I had already run some resource-intensive simulations and now I can't find out how to do a conversion. I'd even run the simulations again, but it seems there's no alternative to using it in CP2K. So I think the answer to your first question is yes. I can't answer your second question. Good luck.

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Hossam Elgabarty

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Jul 14, 2020, 11:15:45 AM7/14/20

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Hi Pierre,

is the dipole moment computed by FIST with the Berry Phase method the same thing as what is commonly called the Berry Phase?

Yes, it is based on the Berry phase formulation of polarization.

Furthermore, when using the polarizable forcefield, are the induced dipoles involved in the calculation of the Berry Phase dipole moment?

To my knowledge, in the core-shell model, the charge used to compute the dipole is simply the sum of the core+shell charges of each atom. I don't know about the case for self-consistent polarizable dipoles and multipoles.

Regards,

Hossam

Nt

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Jul 14, 2020, 12:04:03 PM7/14/20

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Dear Hossam:

I hope I am not being too forward in hijacking Pierre's post. Do you know if it is possible not to us Berry Phase? Or to do a conversion subsequently? Thank you for any advice.

Hossam Elgabarty

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Jul 14, 2020, 12:59:10 PM7/14/20

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Dear Nt,

Do you know if it is possible not to us Berry Phase? Or to do a conversion subsequently? Thank you for any advice.

Yes, check out this section of the input manual:

CP2K_INPUT /
               FORCE_EVAL /
               DFT /
               EFIELD

You cannot do a "conversion" subsequently after the simulation, you have to run new simulations.

Regards,

Hossam

Nt

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Jul 14, 2020, 2:39:54 PM7/14/20

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Dear Hossam,

Thank you very much indeed. I'm relieved there's a solution. Would you mind if I prepared an input file and ran it by you next week?

Regards, Nt.

Hossam Elgabarty

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Jul 15, 2020, 6:43:08 AM7/15/20

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Dear Nt,

Looking back at your previous questions, I think I might have misunderstood what you meant. If your question is about _printing_ the dipole moment using a non-periodic position operator, then you can simply choose:

PERIODIC .FALSE.

in this section:

https://manual.cp2k.org/cp2k-7_1-branch/CP2K_INPUT/FORCE_EVAL/PROPERTIES/LINRES/LOCALIZE/PRINT/TOTAL_DIPOLE.html

Of course you can always do this on snapshots extracted from the trajectory. Whether this is eventually consistent or not with your choice of boundary conditions is upon you to decide.

Best regards,

Hossam

Thomas Kühne

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Jul 15, 2020, 10:03:21 AM7/15/20

to 'Dorothea Golze' via cp2k

Let me add that a particular easy introduction to the „modern theory of polarization“ that

I enjoyed a lot is: https://www.sciencedirect.com/science/article/pii/S0022459612003234

It’s implementation within CP2K is well described in:

https://aip.scitation.org/doi/abs/10.1063/5.0007045%40jcp.2020.ESS2020.issue-1

Best,

Thomas

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Thomas D. Kühne

Dynamics of Condensed Matter

Chair of Theoretical Chemistry

University of Paderborn

Warburger Str. 100

D-33098 Paderborn

Germany

tdku...@mail.upb.de

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