# Crystalline AlP - rhombohedral distortion imposed
# Piezoelectroc tensor calculation

  ndtset  4

#First dataset : Self-consistent ground-state run

 kptopt1  1

#Second dataset :  Non-self-consistent run for full k point set

   iscf2  -2
 getden2  1
 getwfk2  1

#Third dataset : finite-difference d/dk ground-state calculation
#                uses bdberry_new

berryopt3  -2
  getwfk3  2
  getden3  1
    iscf3  -2
   rfdir3  1 1 1

#Fourth dataset : electric field and strain response

 getwfk4  2
 getddk4  3
  rfdir4  1 0 0
 rfelfd4  3
 rfstrs4  3
 diemix4  0.85
 diemac4  1.0

# Common data

   acell  3*10.30
  diemac  6.0
    ecut  4.0
  kptopt  3
   natom  2
   nband  4
  nbdbuf  0
   ngkpt  4 4 4
 nshiftk  1
   nstep  60
  ntypat  2
  occopt  1
  prtden  1
  prtvol  10
   rprim  0.05 0.55 0.55
          0.55 0.05 0.55
          0.55 0.55 0.05
  shiftk  0.5 0.5 0.5
    xred  3*0.00d0 3*0.25d0
  tolwfr  1.d-12
   typat  1 2
   znucl  13 15

 pp_dirpath "$ABI_PSPDIR/PseudosHGH_pwteter"
 pseudos "13al.3.hgh, 15p.5.hgh"

#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test = 
#%%   t66.out, tolnlines = 36, tolabs = 5.000e-04, tolrel = 1.001e+00, fld_options = -easy 
#%% [paral_info]
#%% max_nprocs = 10
#%% [extra_info]
#%% authors = D. R. Hamann
#%% keywords = NC, DFPT
#%% description = 
#%%   Test of the strain perturbation for the rigid-ion piezoelectric
#%%   tensor.  Rhombohedrally distorted
#%%   AlP as in the previous test, but using a ground-state finite-
#%%   difference calculation of the d/dk wave functions.  Such
#%%   calculations were used extensively to test the response function
#%%   piezoelectric tensor by comparison to numerical derivatives of
#%%   the ground-state polarization.  Using the same k sample in the
#%%   ground state and response function calculations, excellent
#%%   agreement has been obtained in a variety of cases (including a
#%%   better-converged version of this one).  Results using the finite-
#%%   diffrence d/dk and the analytic d/dk as in the preceeding test
#%%   agree in the limit of large k sample. The analytic form converges
#%%   much more rapidly, and is consistent with the slowly converging
#%%   polarization numerical derivatives. The present version of this
#%%   calculation uses berryopt = -2 to utilize the routine
#%%   berryphase_new.f
#%%   The ground-state polarization calculations used to compute the
#%%   numerical derivatives in such tests should also be computed using
#%%   berryphase_new.f setting berryopt = -1 and rfdir = 1 1 1 so that the
#%%   cartesian polarization is automatically generated. This eliminates
#%%   several issues that needed special attention using berryopt = 1
#%%   and the original berryphase.f routine.
#%%   The resulting cartesian polarization derivatives represent the
#%%   "improper" piezoelectric tensor, and have to be corrected to yield
#%%   the "proper" tensor as described in D. Vanderbilt, J. Phys. Chem.
#%%   Solids 61, 147 (2000), using Eq.(15).  The response-function calculation
#%%   gives the proper piezoelectric tensor.  Only the electron response, and
#%%   not the strain-induced movement of the rigid ions contributes to the
#%%   proper tensor.
#%% topics = Berry, DFPT
#%%<END TEST_INFO>