?Dear Sir,
I have checked the k -point sampling for the tetragonal PbTiO3 and
I hope that the k-point sampling is alright. I am giving below the input file
for your reference. Pl, let me know if anything is wrong in the input.:
THE I/P FILE FOR TETRAGONAL PbTiO3
&CONTROL
calculation = 'nscf'
pseudo_dir = '/home/nbaski/espresso-4.0/pseudo/'
outdir = '/home/nbaski/tmp/'
lberry = .true.
gdir = 3
nppstr = 7
/
&SYSTEM
ibrav = 6
celldm(1) = 7.3415
celldm(3) = 1.0653
nat = 5
ntyp = 3
nbnd = 22
ecutwfc = 30.0
occupations = 'fixed'
degauss = 0.00
/
&ELECTRONS
conv_thr = 1e-5
mixing_beta = 0.3
/
ATOMIC_SPECIES
Pb 207.2 Pb.vdb.UPF
Ti 47.867 Ti.vdb.UPF
O 15.9994 O.vdb.UPF
ATOMIC_POSITIONS
Pb 0.00000 0.00000 0.01000
Ti 0.50000 0.50000 0.53770
O 0.50000 0.50000 0.11180
O 0.00000 0.50000 0.61740
O 0.50000 0.00000 0.61740
K_POINTS {automatic}
4 4 7 1 1 1
Thank you in advance for any help
SATHYA SHEELA.S
Grad. Student
Department of Physics
National Institute of Technology
Tiruchirapalli
On Fri, 27 Jun 2008 Stefano Baroni wrote :
>the sum of the all the effective charges should be zero for any structure,
>due dynamical charge neutrality (or acoustic sum rule, or whatever you want
>to call the fact that a homogeneouse electric field will not exert a net (and
>infinite!) force on a crystal. Vioation of this charge neutrality/acoustic
>sum rule are often due to numerical inaccuracy, often inaccurate k-point
>sampling. you may want to check the convergence of your calculations with
>respect to the number of k points and/or try to calculate the effective
>charges using linear- response theory. SB
>
>On Jun 27, 2008, at 11:51 AM, sathya subramanyan wrote:
>
>>
>>Dear Developers,
>> I am trying to calculate the Berry Phaze Polarization and
>> effective charge on Pb(with the displacement of . 01*ao) for
>> PbTiO3(tetragonal) but am getting a negative value, using quantum espresso
>> ver 4.0.
>>
>> When I run the example 10 for cubic phase the polarization
>> and the Z* comes out to be alright. But, when I try for tetragonal phase, I
>> am getting negative ionic phase leading to negative polarization for Pb.
>> If I compare the out put file for both cubic and
>> tertragonal phase, to my surprise in the cubic phase the total ionic phase
>> comes out to be positive (actually, if you sum it is negative), where as in
>> the case of tetragonal phase the ionic phase comes out to be negative (but,
>> it is positive if you sum the same way as for the cubic).
>> I do not understand this differrent summing rule for
>> different phases. I am attaching both the input and out files for cubic and
>> tetragonal phases. I would appreciate any useful suggestions to clear this
>> point.
>>I am very sorry for the long mail and data files.
>>
>>- 620015
>>India
>>
>>_______________________________________________
>>Pw_forum mailing list
>>Pw_forum at pwscf.org
>>http://www.democritos.it/mailman/listinfo/pw_forum
>
>---
>Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste
>http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /
>stefanobaroni (skype)
>
>La morale est une logique de l'action comme la logique est une morale de la
>pens?e - Jean Piaget
>
>Please, if possible, don't send me MS Word or PowerPoint attachments
>Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
>
>
>
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
http://www.democritos.it/pipermail/pw_forum/attachments/20080708/5d6ee9f7/attachment.htm
