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[<mozhganamini@yahoo.com>]

Dear all,
I'm trying to calculate the elastic constants of PbTiO3 for comparing the
results with:  " Y. Liu et al. , Materials Science and Engineering A 472(2008)
"
but my results are approximately twice the results in this article!?
Thanks a lot in advance

my results for elastic            results in article
C11: 629 (GPa)                               383
C12: 192                                         151 
C44: 116                                         120

my input file:

 acell  3*3.863 angstrom
 rprim 1.0  0.0  0.0 
           0.0  1.0  0.0   
           0.0  0.0  1.0          
#Definition of the atom types and atoms
 ntypat   3 
 znucl   82 8 22
 natom   5
 typat   1 3 2 2 2

  xred  0.0    0.0    0.0
        0.5    0.5    0.5
        0.5    0.5    0.0
        0.5    0.0    0.5
        0.0    0.5    0.5

 nband   13      
              
#Definition of the plane wave basis set
   ecut   45.0   
 ecutsm   0.5        
                         
#Definition of the k-point grid
 kptopt   1          
ngkpt   6 6 6   
nshiftk   1            
 shiftk   0.5 0.5 0.5   
           
#Definition of the self-consistency procedure
 diemac   6.0    
   iscf   5             
  nstep   100