[DFTB-Plus-User] Clarification on warnings requested

[Benjamin Hourahine]

Hello Sebastiaan,

Changes in the dipole moment are well defined in this case, but not the absolute value.

The warnings are coming from different physical effects:

For electrically charged systems, the total dipole moment depends on the origin of the coordinate system. You could impose a convention, such as placing the centre of charge at the origin.

For periodic systems, again changes in origin change the value, but this also applies to neutral systems. Again differences (modulo transfers by lattice vectors, see for example https://doi.org/10.1103/RevModPhys.66.899) are well defined.

Regards

Ben

       Dr. B. Hourahine, SUPA, Department of Physics,
     University of Strathclyde, John Anderson Building,
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     +44 141 548 2325, benjamin.hourahine at strath.ac.uk

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________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of Sebastiaan Hermans <S.A.H.Hermans at student.tudelft.nl>
Sent: 19 May 2022 21:57
To: dftb-plus-user at mailman.zfn.uni-bremen.de <dftb-plus-user at mailman.zfn.uni-bremen.de>
Subject: [DFTB-Plus-User] Clarification on warnings requested

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Dear,



Since I last updated DFTB+, I am receiving these warnings:



WARNING!

-> Dipole printed for a charged system : origin dependent quantity

WARNING!

-> Dipole printed for extended system : value printed is not well defined



I am simulating a periodic system containing a copper sheet electrode with a negative charge and a large set of point charges.

Could you help me understand these warnings? Is the last warning to attend me to the self-interaction of the point charges in the periodic system?



Kind regards,

Sebastiaan

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