#Test strain perturbation.  Si crystal, finite difference and response
#function 2DTE wrt strain are compared.

ndtset 12

#First dataset : self-consistent run with limited convergence
tolvrs1 1.0d-12

#Datasets 2-6 : finite-difference runs with strain component 1 (xx)
# increment 0.00002

getwfk2 1
rprim2
    0.000000    0.500000    0.500000
    0.499980    0.000000    0.500000
    0.499980    0.500000    0.000000

getwfk3 1
rprim3
    0.000000    0.500000    0.500000
    0.499990    0.000000    0.500000
    0.499990    0.500000    0.000000

getwfk4 1
rprim4
    0.000000    0.500000    0.500000
    0.500000    0.000000    0.500000
    0.500000    0.500000    0.000000

getwfk5 1
rprim5
    0.000000    0.500000    0.500000
    0.500010    0.000000    0.500000
    0.500010    0.500000    0.000000

getwfk6 1
rprim6
    0.000000    0.500000    0.500000
    0.500020    0.000000    0.500000
    0.500020    0.500000    0.000000

#Datasets 7-11 : finite-difference runs with strain component 4 (yz)
# increment 0.00002

getwfk7 1
rprim7
    0.000000    0.499990    0.499990
    0.500000   -0.000010    0.500000
    0.500000    0.500000   -0.000010

getwfk8 1
rprim8
    0.000000    0.499995    0.499995
    0.500000   -0.000005    0.500000
    0.500000    0.500000   -0.000005

getwfk9 1
rprim9
    0.000000    0.500000    0.500000
    0.500000    0.000000    0.500000
    0.500000    0.500000    0.000000

getwfk10 1
rprim10
    0.000000    0.500005    0.500005
    0.500000    0.000005    0.500000
    0.500000    0.500000    0.000005

getwfk11 1
rprim11
    0.000000    0.500010    0.500010
    0.500000    0.000010    0.500000
    0.500000    0.500000    0.000010

#Dataset 12 : response function strain perturbation calculation
  rfstrs12  3
   rfdir12  1 0 0
    nqpt12  1
     qpt12  0 0 0
  kptopt12  2
  getwfk12  4

#Common input variables
 acell  3*10.244431285 #previously optimized
 diemac 12.0
 ecut  6.0
 ecutsm  0.5
 kptopt 1
 natom 2
 nband  4
 ngkpt 2 2 2
 nloc_alg 3
 nshiftk 4
 nstep  30
 ntypat 1
 prtvol  1
 rprim  0.000  0.500  0.500
        0.500  0.000  0.500
        0.500  0.500  0.000
 shiftk 0.5 0.5 0.5
        0.5 0.0 0.0
        0.0 0.5 0.0
        0.0 0.0 0.5
 tolvrs 1.0d-20
  typat 1 1
 xred    0.0   0.0   0.0
         0.25  0.25  0.25
 znucl  14

 pp_dirpath "$ABI_PSPDIR"
 pseudos "PseudosTM_pwteter/14si.pspnc"

#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test = 
#%%   t61.out, tolnlines = 0, tolabs = 9.984e-09, tolrel = 6.000e-04, fld_options =  -medium
#%% [paral_info]
#%% max_nprocs = 2
#%% [extra_info]
#%% authors = D. R. Hamann
#%% keywords = NC, DFPT
#%% description = 
#%%   Test of the strain perturbation.
#%%   Si in the usual diamond structrure using a Troullier-Martins
#%%   potential including a model core charge.  The datasets
#%%   include an initial ground state run, 2 pairs of 5 ground
#%%   state runs with incrementally strained lattice vectors rprim
#%%   (xx and yz strains -0.00004, -0.00002, 0, 0.00002, 0.00004),
#%%   and one response function run for the strain 2nd derivatives.
#%%   This set is illustrative of the kind of testing used extensively
#%%   in developing the strain perturbation portions of the code.
#%%   The numerical 2nd derivatives of the energy wrt strains were
#%%   computed by applying a 5-point derivative formula to ucvol*sigma(i,j),
#%%   where the sigmas are the stresses calculated in the series
#%%   of ground state calculations.  These agree with the analytic
#%%   2nd derivatives calculated in the response function run to ~1.E-7
#%%   for the data given here.  The cartesian internal strain (mixed
#%%   second derivative wrt strain and atomic coordinate) agrees to ~1E-8.
#%%   Note that such numerical tests of the internal strain are only valid
#%%   if the forces are zero (relaxed or by symmetry).  Otherwise, the
#%%   reduced-coordinate 2nd derivatives must be used for such tests
#%%   because the conversion to cartesian coordinates is itself strain-
#%%   dependent and will introduce changes in the computed derivatives.
#%%   In the actual development tests, stricter converence criteria were
#%%   used (tolvrs=1.E-24) as well as larger cutoffs, and agreement was
#%%   obtained at the 1.E-9 level.  The model core charge contributes the
#%%   largest component of the error.
#%%   ADDITIONAL NOTE :
#%%   It should be noted that numerical derivative tests of the internal
#%%   strain should be done by comparing the "2nd-order matrix" with numerical
#%%   strain derivatives of the gradients wrt reduced atomic coordinates.
#%%   These are not normally part of the GS output, but can be obtained by
#%%   uncommenting the DEBUG section at the end of prtxf.F90.
#%%   Comparisons between numerical strain derivatives of the cartesian
#%%   forces and the cartesian internal strain tensor will be incorrect
#%%   unless the coordinates have been relaxed and the forces are zero
#%%   within a tight tolerance.
#%%<END TEST_INFO>