[Pw_forum] symmetry of the electron-phonon coupling coefficients
alex.kutana at gmail.com
Fri May 11 00:10:31 CEST 2012
Thank you for your explanation.
I incorrectly assumed that translation should leave the matrix element
invariant, which is false, since wavefunctions actually stay fixed.
Thanks again for your help.
On Thu, May 10, 2012 at 4:56 PM, Stefano de Gironcoli <degironc at sissa.it>wrote:
> dear Alex
> I don't think that the two matrix element should be equal and opposite.
> suppose you apply both displacement together which means you displace
> the molecule as a whole.
> the eigenvalue will not change, hence < i | dV | i > = 0
> but the new eigen-wavefunctions | i' > will be the translated of the
> original ones, hence different from them.
> to first order |i'> = |i> + sum |j> <j|dv|i>/delta e_IJ
> since |i'> =/= |i> no reason to believe that < j | d V | i > = 0.
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the users