The ABINIT Users Mailing List ( CLOSED )

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

Dear Annie,

I ran a a version of your data with scaled-down cutoffs appropriate to 
valence-only GaAs psp's, and got -0.186 C/m^2, not that different from 
your result.  Then I looked for an experimental value, and found it to 
be -0.16 C/m^2.  So, I don't think there is a problem, and I'm not sure 
what you're looking at that is off by a factor of 82.  I'm attaching a 
tarball with my input data and the anaddb output.

Best regards,
Don Hamann

annie_beya@yahoo.fr wrote:
> Dear all,
>
> I have been trying to compute the piezoelectric tensor of GaAs (following the
> tutorial and the test case tK).
> 1. I am using abinip 5.6.5 and the fhi pseudopotentials 31-Ga.LDA.fhi and
> 33-As.LDA.fhi
> I got the ddb files and analysed them with anaddb. but the value that i get 
> for
> the piezo constant is -0.23C/m2 that is 82 times higher than the expected
> value.
>
> I had some convergence problems for the ddk calculation then i used nline and
> iprcel, following some suggestions from this forum. could somebody have a look
> on my input file (see below) and tell me what could be wrong? the values that 
> i
> use for acell and ecut are the converged values.
>
> 2. Using the semi-core electrons as valence electrons (again the fhi psp with
> 3d electrons for Ga) gave me optimized values for the lattice parameters that
> are very close to theoretical ones (I mean a precision of 0.1%). But I could
> not perform any response function calculation to get the piezo constant, again
> due to convergence problems and band filling. I tried the solutions provided 
> to
> other users, but they did not help. I thought maybe there are better psp to be
> used or better ways. Do you have any suggestions?
>
> 3.I will use the berry phase formulation of the polarisation to get the piezo
> constants. I am doing response function to compare results from both
> calculations (berry phase approach and response function) and I would like to
> be sure i am using the good parameters and understand how abinit works.
>
> 4. I noticed this warning that comes quite often and i followed the 
> suggestions
> on the forum to set the same kptopt to both ground state calculations and
> response function calculations. but it did not help, and induced other
> troubles. Is this warning critical? What can I do to solve the problem?
>
> hdr_check: WARNING -
> -P-0000   input nkpt=    6912 not equal disk file nkpt=     182
> hdr_check: WARNING -
> -P-0000   Restart of self-consistent calculation need translated 
> wavefunctions.
> -P-0000   Indeed, critical differences between current calculation and
> -P-0000   restart file have been detected in:
> -P-0000         * the number, position, or weight of k-points
> -P-0000         * the format of wavefunctions (istwfk)
>
> thanks for your reply,
>
> Annie
>
> #GaAs in zincblende structure
>
> ndtset 3 
> jdtset 1 2 3 
> # Set 1 : initial self-consistency
>
> kptopt1   1
> tolvrs1 1.0d-18
> iscf1 5
>
> #set 2 the ddk 
> rfelfd2 2  # only derivative of the gs wf
> rfdir2 1 1 1
> nqpt2 1
> qpt2 0.0 0.0 0.0 #only the gamma point
> getwfk2 1
> getddk2 2
> kptopt2 3
> iscf2 -3
> tolwfr2 1.0d-20
>
> # Set 3 : response-function strain calculation
>
> rfphon3 1
> rfatpol3 1 2 
> rfelfd3 3
> rfdir3 1 1 1
> nqpt3 1
> qpt3 0 0 0
> rfstrs3  3
> getwfk3 1
> getddk3 2
> kptopt3 3
> tolvrs3 1.0d-16
> iscf3 5
>
> #common input data
> paral_rf 1 # activate parallelization over perturbations
> ngroup_rf 2 # number of groups for  parallelization over perturbations
>
>    ecut   50.0
>    iscf   5
>    diemac 12.0
>    iprcel 49
>    nline 15
>
>    ixc    7
>   nband   8
>   occopt 1
>
>   ngkpt   12 12 12
>   nshiftk   1
>   shiftk   0.0 0.0 0.0
>   nstep   200
>
>   acell    3*10.5 # this is the optimized value
>   rprim  0.0  0.5  0.5
>        0.5  0.0  0.5
>        0.5  0.5  0.0
>   natom   2
>  ntypat   2 
>   znucl  31 33
>   typat   1 2
>    xred   0.0 0.0 0.0
>           1/4 1/4 1/4
>
>   

--
D. R. Hamann
Mat-Sim Research LLC    | Department of Physics
P.O. Box 742            |  and Astronomy
Murray Hill, NJ 07974   | Rutgers University
phone: 908-370-8079     | 732-445-5500, x4381

email: drhamann@mat-simresearch.com

Attachment: GaAs_piezo.tar.gz
Description: GNU Zip compressed data