[CP2K:474] berry phase

Fawzi Mohamed fa... at gmx.ch
Tue Dec 11 00:04:13 CET 2007


Hi Marc,

Berry Phase is needed for periodic boundary conditions.
Indeed it is not anymore possible to use just x,y,z as positions  
because then you have a discontinous jump somewhere.
One solution is to work with with the phase of complex numbers, as  
that has the correct circular topology.
Basically you go from position to complex phase doing
	exp(i*2Pi x)
where is x is the first component in reduced units. You do the same  
for the other two components.
you calculate the dipole using these complex numbers, and *at the  
end* you go back taking the logarithm (phase).

For literature references with respect to classical MD, I do not  
know, someone should chime in, I know it from polarization in  
abinitio...

Fawzi
On Dec 10, 2007, at 5:41 PM, marc wrote:

>
> Hey all,
>
> I have a problem concerning the calculation of dipole moments in
> cp2k.  I'm doing classical  molecular mechanics using force fields, so
> can I use cp2k for this?  What we want to do is calulate an IR-
> spectrum using M.D..  I already ran a calculation, and cp2k gives
> three dipole moments for each simulation step:
>
> 1. MM DIPOLE BERRY PHASE ( A.U.)|
> 2. MM DIPOLE BERRY PHASE (Debye)|
> 3. MM DIPOLE (NON BERRY PHASE) DERIVATIVE (A.U.)|
>
> Has the berry phase output any revelance when doing classical M.D.
> using force fields?  I also was wondering what the berry phase
> actually has to do with dipole moments?  Can someone give a reference
> which explains this berry phase related to classical M.D.?
>
> regards,
>
> marc
>
>
> 



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