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[Wei-Bing Zhang <zwb256@hotmail.com>]

Dear abinit users!
     I am a new user of abinit. As a test , I want to use DFFT of abinit to
calculated the elastic constants of fcc Ni. Following the example provided in
"elastic" lesson of the tutorial:, Firstly , perform a optimization of acell,
following by GS calculation. third perform a Non-self-consistent GS .finally ,
perform a RF run for symmetry-inequivalent elastic constants. And the getcell 
 
-1 is used in last three steps.  however,  When I check the *.out, I found 
that
the getcell work well in step 2 and step4 but became valid in step 4. in step
4, I found the acell is not read from the output of step 3 but come from the
input of step 1. Is "getcell" valid in RF calculations??
   And, I cannot get reasonable elastic constant results of Ni. First, i 
always
get the negative constants. When I increase the "ecut" and Kpoints mesh, I get
c11  127.73978170477126  c12 97.034604419461246  c13  6.812321968597402  which
is only half of experimental value. Can you help what wrong about my input
file. How can I get the reasonable elastic results based on DFFT. Thanks you.
any suggestions about calculations of Ni will be appreciated!!
 Wei-Bing Zhang
 zwb256@hotmail.com 
===================================================================
#Al fcc metal - elastic constant calculation

   ndtset   4       # Total number of datasets (3*4)
  dilatmx=1.5

# Set 1 : Initial self-consistent and lattice optimization run

  getwfk1   0
  ionmov1   2        # Broyden lattice optimization scheme
   ntime1   50        # Maximim lattice optimization steps
 optcell1   1        # Optimize cell volume only
 strfact1   100      # Test convergence of stresses (Hartree/bohr^3) by
                      # multiplying by this factor and applying force
                      # convergence test
  tolmxf1   1.0e-6   # Convergence limit for forces as above
  tolvrs1   1.0d-18  # Need excellent convergence of GS quantities for RF runs
#set 2
 prtden2   1        # Third dataset needs density
  tolvrs2   1.0d-18

# Set 3 : Converge unoccupied wave functions

  getden3   -1       # Use density from previout set
  tolwfr3   1.0d-30  # This is simply for a reason of portability of automatic
tests 
  nstep3  45

# Set 4 : response-function calculations for all needed perturbations

  kptopt4   2        # Time-reversal only for RF calculation
    nqpt4   1
     qpt4  0  0  0  # By symmetry, only need one direction
   rfdir4   1  0  0
  rfstrs4   3        # Need both unaxial and shear strains
  tolvrs4   1.0d-12  # Need reasonable convergence of 1st-order quantities

#Common input data

#Double loop data passing

#getcell   -1         # Start from optimized (datasets ?2-?4) or previously
                     # optimized (datasets ?1) acell
 getwfk   -1         # Use last set of wave functions (except datasets ?1)


getcell   -1 

nband=8
#Definition of the plane wave basis set
 ecutsm   0.5            # Smoothing energy needed for lattice parameter
                         # optimization.  This will be retained for
                         # consistency throughout.

#Definition of the k-point grid - loop over 3 k-point densities
 kptopt   1              # Use symmetry and treat only inequivalent points

#ngkpt1?   6  6  6          
ngkpt   8  8  8          
#ngkpt3?   10 10 10

nshiftk   4              # Use one copy of grid only (default)
 shiftk   0.0 0.0 0.5    # This gives the usual fcc Monkhorst-Pack grid
          0.0 0.5 0.0
          0.5 0.0 0.0
          0.5 0.5 0.5

ecut 1000 eV
#Definition of occupation numbers
occopt 7
tsmear 0.01


#spin related quantities
 spinat   0.0 0.0 1.0
 nsppol   2


#Definition of the unit cell
acell 3*6.7713705382          # This is equivalent to   7.60 7.60 7.60
rprim  0.0  0.5  0.5   # FCC primitive vectors (to be scaled by acell)
       0.5  0.0  0.5 
       0.5  0.5  0.0


#Definition of the atom types
ntypat 1          # There is only one type of atom
znucl 28          # The keyword "znucl" refers to the atomic number of the 
                  # possible type(s) of atom. The pseudopotential(s) 
                  # mentioned in the "files" file must correspond
                  # to the type(s) of atom.
                         

#Definition of the atoms
natom 1           # There is only one atom per cell
typat 1           # This atom is of type 1, that is, Aluminum
xred              # This keyword indicate that the location of the atoms
                  # will follow, one triplet of number for each atom
   0.0  0.0  0.0     # Triplet giving the REDUCED coordinate of atom 1.



#Exchange-correlation functional
ixc 11             # GGA, Perdew-Burke-Ernzerhof GGA functional

#Definition of the SCF procedure
nstep 60          # Maximal number of SCF cycles
                  # between two consecutive evaluations of total energy 
                  # differ by less than toldfe (in Hartree) 
========================================================================
== DATASET  1
==================================================================

 Real(R)+Recip(G) space primitive vectors, cartesian coordinates
(Bohr,Bohr^-1):
 R(1)=  0.0000000  3.3856853  3.3856853  G(1)= -0.1476806  0.1476806  
0.1476806
 R(2)=  3.3856853  0.0000000  3.3856853  G(2)=  0.1476806 -0.1476806  
0.1476806
 R(3)=  3.3856853  3.3856853  0.0000000  G(3)=  0.1476806  0.1476806 
-0.1476806
 Unit cell volume ucvol=  7.7619305E+01 bohr^3
 Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01 degrees

 getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
         ecut(hartree)=     82.686   => boxcut(ratio)=   2.04088
== DATASET  2
==================================================================

 mkfilename : getwfk/=0, take file _WFK from output of DATASET   1.

 driver : getcell/=0, take acell and rprim from output of dataset with index 
1.

 Real(R)+Recip(G) space primitive vectors, cartesian coordinates
(Bohr,Bohr^-1):
 R(1)=  0.0000000  3.3857125  3.3857125  G(1)= -0.1476794  0.1476794  
0.1476794
 R(2)=  3.3857125  0.0000000  3.3857125  G(2)=  0.1476794 -0.1476794  
0.1476794
 R(3)=  3.3857125  3.3857125  0.0000000  G(3)=  0.1476794  0.1476794 
-0.1476794
 Unit cell volume ucvol=  7.7621178E+01 bohr^3
 Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01 degrees

 getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
         ecut(hartree)=     82.686   => boxcut(ratio)=   2.04086
--------------------------------------------------------------------------------

== DATASET  3
==================================================================

 mkfilename : getwfk/=0, take file _WFK from output of DATASET   2.

 mkfilename : getden/=0, take file _DEN from output of DATASET   2.

 driver : getcell/=0, take acell and rprim from output of dataset with index 
2.

 Real(R)+Recip(G) space primitive vectors, cartesian coordinates
(Bohr,Bohr^-1):
 R(1)=  0.0000000  3.3857125  3.3857125  G(1)= -0.1476794  0.1476794  
0.1476794
 R(2)=  3.3857125  0.0000000  3.3857125  G(2)=  0.1476794 -0.1476794  
0.1476794
 R(3)=  3.3857125  3.3857125  0.0000000  G(3)=  0.1476794  0.1476794 
-0.1476794
 Unit cell volume ucvol=  7.7621178E+01 bohr^3
 Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01 degrees

 getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
         ecut(hartree)=     82.686   => boxcut(ratio)=   2.04086
--------------------------------------------------------------------------------

================================================

================================================================================
== DATASET  4
==================================================================

 mkfilename : getwfk/=0, take file _WFK from output of DATASET   3.

 driver : getcell/=0, take acell and rprim from output of dataset with index 
3.

 Real(R)+Recip(G) space primitive vectors, cartesian coordinates
(Bohr,Bohr^-1):
 R(1)=  0.0000000  3.3856853  3.3856853  G(1)= -0.1476806  0.1476806  
0.1476806
 R(2)=  3.3856853  0.0000000  3.3856853  G(2)=  0.1476806 -0.1476806  
0.1476806
 R(3)=  3.3856853  3.3856853  0.0000000  G(3)=  0.1476806  0.1476806 
-0.1476806
 Unit cell volume ucvol=  7.7619305E+01 bohr^3
 Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01 degrees
 setup1 : take into account q-point for computing boxcut.

 getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
         ecut(hartree)=     82.686   => boxcut(ratio)=   2.04088