[Pw_forum] data structure of wave function and charge density

[Paolo Giannozzi]

yumin qian wrote:

>     I need to write a small program to do some  post-process 
> calculation , and I need to read in the wave function and 
> charge density

modify one of the many codes in PP/ that read from the data file

> But I don't know the data structure of the wave 
> function evc(npwx,nbnd)  or evc(npwx*npol,nbnd) in noncolinear case

evc(i,ibnd): ibnd is the band index, i is the index of plane waves
for the noncolinear case:
   i=1,npw  are plane waves with up spin (polarization 1)
   i=npwx+1,npwx+npw are PW with down spin (polarization 2)
npw depends on the k-point, npwx is the maximum npw

> In LSDA case what about the spin part of wavefunction

in LSDA you have only spin-up or spin-down components. The
number of k-points is doubled and the first set contains
spin-up states, the second set spin-down states. The different
approach between LSDA and noncolinear approaches is somewhat
confusing. LSDA was implemented this way because it was easy
(causing minimal disruption to the codes, originally written
for unpolarized systems) and efficient

Paolo
-- 
Paolo Giannozzi, Democritos and University of Udine, Italy