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

[pc229 at kent.ac.uk]

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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