[Pw_forum] negative lambda

[Aritz Leonardo]

Hello all:

I have been searching the archive to know why am I obtaining negative 
values of lambda and gamma and I don't really understand what is going 
on. As far as I see from the formulas (for gamma and lambda) Shouldn't 
they be positively defined??? for example for gamma, we have: the square 
of the matrix element, 2 deltas, ph-frequencies, and BZ volume.

Even though I may be far from convergence in my opinion all the values 
should be positive.

Thanks a lot
Aritz