[CP2K-user] [CP2K:20667] Re: Calculation of dipole moment using voronoi integration

[Nathalie Smith]

Also one note: With your equation, you are first calculating the magnitude 
of the overall dipole moment, and then divide it by the number of atoms. 
This is not the same as the average magnitude of the atomic dipole moment 
(if that is the value you are looking for - it's not clear for me from your 
first message).

Imagine you have 2 atoms (i and k) in your system, each with an atomic 
dipole moment vector p. The overall dipole moment is the vector sum of the 
two atomic dipole moments: e.g. for the x component, you have: x_overall = 
x_i + x_k. You do the same for the y and z components to obtain the overall 
dipole vector.

You calculate with your equation:
( sqrt( (x_i + x_k)² +  (y_i + y_k)² +  (z_i + z_k)² ) ) / 2 = ( sqrt( 
x_overall² + y_overall² + z_overall²) ) / 2 = | p_overall | / 2.

The average magnitude of the atomic dipole moment, however, would be:
( sqrt( x_i² + y_i² + z_i² ) +  sqrt( x_k² + y_k² + z_k² ) ) /2 = ( | p_i | 
+ | p_k | ) / 2.

| p_overall | is NOT the same as  ( | p_i | + | p_k | ).

>From your first message, it's not clear what you exactly want to calculate 
- The average magnitude of the atomic dipole moment? The magnitude of the 
dipole moment of the whole system (but then, you wouldn't divide the value 
by the atom number)? The dipole moment of the whole system? The average 
atomic dipole moment of the system?

Best wishes, 
Nathalie

Nathalie Smith schrieb am Montag, 9. September 2024 um 15:27:34 UTC+2:

Hello Sagnik,

I am not an expert, but I might be able to help. It seems like you want to 
calculate the mean atomic dipole moment with your equation "magnitude of 
dipole moment=SQRT( (summation of x-component)^2 + (summation of 
y-component)^2 + (summation of z_component)^2)) / number of atoms", right? 
Did you also calculate the mean atomic dipole moment from Wannier 
localization in the same way? By how much do your results from Voronoi 
integration differ from the results from Wannier localization?

Best wishes, 
Nathalie Smith

Sagnik Mukhopadhyay schrieb am Montag, 26. August 2024 um 09:29:17 UTC+2:

Hi CP2K community,

I was running a simulation for a system with Au-H2O, where I was 
calculating the dipole moment of the Au, H2O and overall system using 
Voronoi integration. In the ".voronoi" file there is information about 
charge, position, dipole moment vector, quadrupole moment tensor (component 
wise) etc. To calculate the dipole moment I was using the formula: 
magnitude of dipole moment=SQRT( (summation of x-component)^2 + (summation 
of y-component)^2 + (summation of z_component)^2)) / number of atoms. After 
using this formula the dipole I got is different from the one obtained from 
Wannier localization. Can somebody confirm if this is the formula to 
calculate the dipole moment using Voronoi integration?
Thanks in advance.

Regards
Sagnik

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