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["D. R. Hamann" <drhamann@mat-simresearch.com>]

Dear mozhganamini,

Your input file does not look like an elastic-constants input file.  
Have you done the "Elastic properties" tutorial?  Without the full input 
file that gave these results, it is hard to diagnose your problem.  I 
see no "tol..." input variables, and the convergence criteria to get 
good elastic constant (and other response function) results are much 
tighter than the defaults that your attached ground-state file 
apparently would get.

Don Hamann

mozhganamini@yahoo.com wrote:
> 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	      
>
>   

--
D. R. Hamann
Mat-Sim Research LLC    | Deptartment of Physics
P.O. Box 742            |  and Astronomy
Murray Hill, NJ 07974   | Rutgers University
phone: 908-370-8079     | 732-445-4381

email: drhamann@mat-simresearch.com