The ABINIT Users Mailing List ( CLOSED )

[Matthieu Verstraete <mjv500@york.ac.uk>]

Hi -

The default behavior of abinit is to use a shift of 0.5 0.5 0.5 for the 
kpoints. Check the values in the kpt array of your output. In your case 
this still brings you to the "zone boundary" where the wavefunctions can 
still be chosen as real. The operative word is "can": as you said yourself 
it can have an arbitrary phase.

In our case the psi are stocked in reciprocal space, where this implies 
1/2 the coefficients can be obtained from the other 1/2 using symmetries 
(k -> -k+G), but for k/=Gamma I'm not sure this is equivalent to making 
the choice "psi real". So

1) make sure you really are using Gamma and not L

2) look at the value of istwfk which states how the coeffs are stocked and 
recreated using symmetries. If you set istwfk to 1 and still have your 
problem, and are sure you're using gamma _and_ that it's not just a phase 
shift, then we may have a bug... Possibly in the way the wfk are output. 
You used cut3d? Which mode, etc?

3) Oh, yeah, it may be linked to your choice of unit cell: yours doesn't 
explicitly include inversion symmetry. Use

xred -0.125 -0.125 -0.125
      0.125  0.125  0.125

to be sure. Or try a simpler system (1 atom/UC).

Matthieu

--
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Dr. Matthieu Verstraete                 mailto:mjv500@york.ac.uk
Dept. of Physics, University of York,     tel: +44 1904 43 22 08
Heslington, YO10 5DD York, United Kingdom fax: +44 1904 43 22 14