[Pw_forum] input for resp_mat.x in to optimize the U for LDA+U calculations

[Pieremanuele Canepa]

Dear all,
I was  able to compile  the program resp_mat.f90 in order to  carry out the
U in a self consistent way. Now I am trying to write up correctly the input
for resp_mat.x. I have realized reading trough the guide (found at link
http://vlab.msi.umn.edu/events/lecture.shtml)  that I do need to have an
external file   with the fractional coordinate of the atom belonging to the
supercell.
Actually, if I look at those external file (call for example pos....) that
come togheter with the guide found online, the second part is concerning to
the fractional coordinate of the atoms in the supercell, while what is the
first part? Are these the vector of the supercell in Cartesian coordinates ?
Why, when  for instance  the   Cartesian coordinate of the  supercell
vectors printed in the early part of the PWscf output are:
  crystal axes: (cart. coord. in units of a_0)
               a(1) = (  1.000000  0.000000  0.000000 )
               a(2) = (  0.000000  1.000000  0.000000 )
               a(3) = (  0.000000  0.000000  1.000000 )
in the file pos  these become
20.d0 0.d0 0.d0
0.d0 20.d0 0.d0
0.d0 0.d0 20.d0
?
The cell parameter  in this case is 10.8400 (FeNi in the guide)

Another question is : what does the line   back = 'neutral' mean  in the
input file for resp_mat.x?
I hope  you can get my point!
Best Regards, Piero
-- 
Pieremanuele Canepa
Room 230
School of Physical Sciences, Ingram Building,
University of Kent, Canterbury, Kent,
CT2 7NH
United Kingdom
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