[Pw_forum] Fwd: shape of real space wave functions in wfc2kr

[Lorenzo Paulatto]

On 27/09/17 19:33, Jacopo Simoni wrote:
> Ok many thanks for the reply, and sorry for the delay.
> 2- So you are saying that the wave functions I get are the coefficients 
> u_nk(r) in Psi_nk(r) = u_nk(r) e^ikr . These cannot be used to 
> reconstruct the density in real space because they are on the smooth 
> grid . This smooth grid is always given by the expression
> r_ijk(:) = (i-1)/nr1x * a_1(:) + (j-1)/nr2x * a_2(:) + (k-1)/nr3x * a_3(:) ?

There are several grid, dfftp is the charge density grid (ecutrho) dffts 
is the smooth grid (4*ecutwfc). There is no specific grid for the 
wavefunctions, as they are always put on the smooth grid (in g-space) 
before being fourier transformed.

Also keep in mind that when things are in G-space, their plane-waves 
could be in order of the Fourier transform grid, or in order of 
increasing |G|. There are two integer arrays, nl and nls from modules 
gvect and gvecs that map between these two representations


> This function u_nk(r) does not seem to be normalized, what is the 
> normalization factor ? are these the same wave functions used in the 
> routine hpsi to compute the product with the local part of the potential ?

As far as I know they are normalized, did you include the volume 
element? Volume/nnr

> 
> I am sorry for all these questions, but before using this object I want 
> to be sure what it is exactly. So I really appreciate your effort in 
> answering these question.

No problem, but you may want to tell us what you are trying to do, 
because there is a good chance that is has been done already.

cheers


-- 
Lorenzo Paulatto - Paris