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["waigen zhang" <waigen.zhang@gmail.com>]

Hi,
Thanks for the reply for my last question.
Another problem is that I am getting some results(elastic constant) case sensitive for my material.I used the same structural geometry and same ecut,ngkpt,psp...,but each time the outcomes of elastic constants are quite 
different.BTW,I did  the structural optimization and the optimized structure seems no problem before any calculation.
I notice that there is a warning in the output file

elast9 : WARNING - :
  Acoustic sum rule violation met : the eigenvalues of accoustic mode
  are too large at Gamma point
  increase cutoff energy or k-points sampling.
  The three eigenvalues are:    2.354541E-04    3.769631E-06   -9.936443E-05

and the elastic tensor from two different runs with same input parameters are

Elastic Tensor (relaxed ion) (unit:10^2GP):
  (at fixed electric field boundary condition)
0.5479039  -0.2078001   0.4736602   0.0000000  -0.4454188   0.0000000
  -0.2078002  -1.6226535  -0.1456602   0.0000000
  -0.0503831   0.0000000
   0.4736602  -0.1456602  -1.7632272   0.0000000  -0.8610705   0.0000000
   0.0000000   0.0000000   0.0000000  -0.1100148   0.0000000  -0.0896016
  -0.4454189  -0.0503831  -0.8610705   0.0000000
   0.4057265   0.0000000
   0.0000000   0.0000000   0.0000000  -0.0896016   0.0000000  -0.2808213

 Elastic Tensor (relaxed ion) (unit:10^2GP):
  (at fixed electric field boundary condition)
 -2.4936683  -1.4720537
  -0.7323263   0.0000000   0.4624234   0.0000000
  -1.4720537  -3.5190605  -1.2099844   0.0000000  -0.3453437   0.0000000
  -0.7323263  -1.2099843  -0.5868132   0.0000000   0.0348794   0.0000000
   0.0000000   0.0000000
   0.0000000  -1.1759601   0.0000000  -0.3877170
   0.4624235  -0.3453437   0.0348793   0.0000000  -0.7692686   0.0000000
   0.0000000   0.0000000   0.0000000  -0.3877171   0.0000000  -1.5326429

Attachment is the input 
file.Thanks for you suggestion.

Attachment: telast_21.7GP.in
Description: Binary data