The ABINIT Users Mailing List ( CLOSED )

["Mihir Sen" <mihirsen_01@rediffmail.com>]

Dear Yukihiro Okuno and Occupier Liu,

I agree that the piezoelectric constants are changing with structure. For PbTiO3 kpoint 444 mesh is not enough and 666 and 888 k-pointmesh needed. The structure changes and also piezoelectricity. You can start with the 444 optimise structure and incresse k-point grid. see Wu, Cohen and others  Phys. Rev. Lett. 94, 069901 (2005) for correct piezoelectricity constants. Also increase ecut. It will be nice if Wu can send his input file. He posted ABINIT results also.

Mihir Sen
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On Mon, 14 Mar 2005 yukihiro_okuno@fujifilm.co.jp wrote :
>Dear occupierliu.( Is it your name??)
>
>I'm Yukihiro Okuno.
>
>I also calculated piezoelectric tensor.
>I found the atomistic potision and lattice parameter
>influenced the results very much, and I cannot get
>experimental and other publiched value of piezoelectric
>(PRL vol59 p12771)coefficient yet.
>So you must pay attention of the atomic position, and your
>atomic potision seems not optimized one.
>
>Here is my input file.
>Conversed but not good values.
>
>
># Piezoelectroc tensor calculation
>
>ndtset  3
>
>#First dataset : Self-consistent ground-state run
>
>iscf1  5
>kptopt1  1
>tolvrs1 1.0d-18
>
>#Second dataset : d/dk response calculation
>rfelfd2 2  # only derivative of the gs wf
>rfdir2  1 1 1
>iscf2 -3
>kptopt2 2
>getwfk2  -1
>nqpt2 1
>qpt2 0.0 0.0 0.0
>tolwfr2 1.0d-20
>
>#Third dataset : stress and  homogeneous electric field response
># and the replacement of the atom potision
>rfphon3 1
>rfatpol3 1 5
>rfelfd3 3
>rfdir3 1 1 1
>nqpt3 1
>qpt3 0 0 0
>rfstrs3  3
>getwfk3 -2
>getddk3 -1
>kptopt3 2
>tolvrs3 1.0d-18
>iscf3 5
>
>#Common Data Definition of the unit cell
>acell      7.3730000000      7.3730000000      7.8522450000
>rprim    1.000000000000    0.000000000000    0.000000000000
>          0.000000000000    1.000000000000    0.000000000000
>          0.000000000000    0.000000000000    1.000000000000
>
>ntypat    3
>znucl 82 8 22
>natom    5
>typat 1 3 2 2 2
>
>xred    0.000  0.000  0.000
>        0.500  0.500  0.549866726014
>        0.500  0.500  0.125821955824
>        0.500  0.000  0.631627681214
>        0.000  0.500  0.631627681214
>
>ecut 50
>ixc 3
>ngkpt 4 4 4
>occopt 1
>nstep 500
>prtvol 10
>diemac 5.2