# Oxygen molecule, treated with varying occupation numbers,
# with LDA.
#    This is to demonstrate a subtlety of the analysis of
#    finite differences : for metallic occupation numbers,
#    RF computation of 2DTE at Gamma, when taking
#    Fermi energy changes (frzfermi=0), will give the same
#    answer than finite-difference of GS computations.
#    However, in order to find a coherent phonon
#    band structure, and perform the Fourier interpolation,
#    it is likely that the Fermi energy must be frozen
#    (debate was running between Dhamann and XG as of 20040821)

 ndtset 5

#GS
 xred1  0.0 0.0  0.11545    0.0 0.0 -0.1155

 xred2  0.0 0.0  0.1155     0.0 0.0 -0.1155

 xred3  0.0 0.0  0.11555    0.0 0.0 -0.1155

#RF
 xred4  0.0 0.0  0.1155     0.0 0.0 -0.1155
  rfphon4  1
 rfatpol4  1 1
   rfdir4  0 0 1
    nqpt4  1
     qpt4  0.0 0.0 0.0
  getwfk4  2
  tolvrs4  5.0d-3

#RF
 xred5  0.0 0.0  0.1155     0.0 0.0 -0.1155
  rfphon5  1
 rfatpol5  1 1
   rfdir5  0 0 1
    nqpt5  1
     qpt5  0.0 0.0 0.0
  getwfk5  2
  tolvrs5  5.0d-3
frzfermi5  1


#Common data

 diemac 1.0d0
 diemix 0.33333d0
 ecut 13.00
 getwfk -1
 ixc 1
  kptopt 0
 kpt   3*0.0
 natom  2
 nband 12
 nkpt 1
 nstep 30
 nsym 1
 ntypat  1
 occopt 7
 acell  6.500  6.500  9.000
 rprim 1 0 0  0 1 0  0 0 1
 tolvrs 1.d-16
 tsmear 0.02
 typat  1 1
 wtk  1
 znucl  8.0

 pp_dirpath "$ABI_PSPDIR"
 pseudos "PseudosTM_pwteter/8o.pspnc"

#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test = 
#%%   t75.out, tolnlines = 0, tolabs = 0.000e+00, tolrel = 0.000e+00, fld_options = -easy
#%% [paral_info]
#%% max_nprocs = 1
#%% [extra_info]
#%% authors = Unknown
#%% keywords = NC, DFPT
#%% description = 
#%%   O2 (non-spin-polarized, non-linear XC core correction, LDA)
#%%   Metallic occupation numbers.
#%%   For metallic occupation numbers,
#%%   RF computation of 2DTE at Gamma, when taking
#%%   Fermi energy changes (frzfermi=0), will give the same
#%%   answer than finite-difference of GS computations.
#%%   However, prior to v4.4, the change of Fermi energy
#%%   due to the perturbation was not computed.
#%%   This corresponds to calculations performed with frzfermi=1
#%%   (should be used only for testing purposes).
#%%   In dataset 1-3, one computes the total energy and forces,
#%%   without symmetries, as it should be
#%%   for accurate finite-difference tests.
#%%   The reduced gradients with respect to displacements
#%%   of the first atom along z in datasets 1 and 3 are
#%%   -5.705344113253 Ha and -5.692553418498 Ha, giving
#%%   the 2DTE of 127.90 Ha.
#%%   In dataset 4, RF is computed with the Fermi energy correction, 
#%%   and the agreement with finite-differences of datasets 1 and 3 
#%%   is good : one gets 127.9068 Ha .
#%%   In dataset 5, RF is computed with frozen Fermi energy
#%%   and the disagreement with
#%%   finite-differences of datasets 1 and 3 is large:
#%%   one gets 100.9991668 Ha .
#%%<END TEST_INFO>