[Pw_forum] PW.x homogeneous electric field berry phase calculation in trigonal cell

[Lorenzo Paulatto]

On Wednesday, February 8, 2017 5:46:25 PM CET Louis Fry-Bouriaux wrote:
>     In your last email you mentioned the field 'pdir', I have not been able
> to find this in the documentation, is this what you meant? 

It is the internal name of a variable in the subroutine that computes the 
macroscopic polarisation, but I think it is always gdir in the end.

> as this is where the error is when I use other than gdir=3 (I added ln 364
> to identify what fails exactly)

I never did this myself, but from the code expects strings of k-points, one 
after each other. Each string is formed by nppstr k-points, aligned in the 
direction gdir; there can be as many string as you want, in principle to form 
a grid in the two directions orthogonal to gdir.

Maybe in the case gdir=3 these string are formed "spontaneously" when using k-
points automatic, but it does not work in the other cases. The polarisation 
(berry=.true.) and the electric field (lefield=.true.) codes are very similar, 
but not identical, in theory the second is more general, I'm not too familiar 
with either.

I've noticed that you set nosym=.false., I'm quite sure that that swith is 
overridden with lefield, but to be sure, could you try to sisable it?