[Pw_forum] dipole moment calculation
Aihua Zhang
zah7903 at gmail.com
Mon Mar 9 16:39:56 CET 2009
Dear Giovanni,
Thank you for the reply! I have used lelfield option, and you used telfield.
The documentation for telfield (saw_tooth potential) in input_pw.html seems
different from README (modern theroy of polarizaiton) in example30. What's
the difference between these two methods? You maybe should also pay
attention to the units. I found at least in the subroutine related to
lelfield they use Rydberge atomic units, that is, the unit for dipole is
e/sqrt(2)*bohr_radius. In your arithemetic, the Hartree atomic units is
used.
Best regards
Aihua
On Mon, Mar 9, 2009 at 10:19 PM, Giovanni Cantele <
Giovanni.Cantele at na.infn.it> wrote:
> Aihua Zhang wrote:
>
>> Dear all,
>>
>> I tried a test calculation of the dipole moment of water. The water
>> molecule is put into a 20 a.u. ^3 box. The relevant setting are
>>
>> lelfield = .true.
>> efield = 0.01
>>
>> In the output file, it reports
>>
>> Electronic Dipole per cell (a.u.) -1.921145549061207
>> Ionic Dipole per cell (a.u.) 116.1997104738884
>>
>> How is Electronic Dipole defined here? By looking into the source code,
>> Ionic Dipole is defined as in textbook. I also notice that total energy
>> difference with respect to zero-electric-field system is approximately equal
>> to (Electronic Dipole + Ionic Dipole) * Efield. But Electronic Dipole hardly
>> resembles the experimental dipole of water, which is about 1.85 D. Could
>> anyone explain a bit about these quantities? Thank you!!
>>
>> Zhang
>>
>>
>> Hi,
>
> I'm not very expert about this, however I tried to reproduce your job. I
> got:
> Computed dipoles : electron 0.00000
> 0.00000 -4.61164 ion 0.00000 0.00000 -3.87896
> total 0.00000 0.00000 0.73268 Dipole field
> [a.u.]: 0.0012
>
> As far as I understand total dipole moment = 0.73268 a.u. = 0.73268 *
> 25.417463 / 10 Debye = 1.86 Debye.
>
> I remember I found strange results in electric field calculations some time
> ago, and the problem was where the
> molecule is placed within the unit cell, but I'm not very sure (that was a
> couple of years ago!).
> The input I used is in attachment.
>
> Giovanni
>
>
> --
>
>
>
> Dr. Giovanni Cantele
> Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
> Universita' di Napoli "Federico II"
> Complesso Universitario di Monte S. Angelo - Ed. 6
> Via Cintia, I-80126, Napoli, Italy
> Phone: +39 081 676910
> Fax: +39 081 676346
> E-mail: giovanni.cantele at cnr.it
> giovanni.cantele at na.infn.it
> Web: http://people.na.infn.it/~cantele<http://people.na.infn.it/%7Ecantele>
> Research Group: http://www.nanomat.unina.it
>
>
> &CONTROL
> calculation='scf'
> title='H2Otest'
> verbosity='high'
> restart_mode='from_scratch'
> nstep=100
> iprint=1
> tprnfor=.true.
> outdir='./tmp/'
> prefix='H2Otest'
> disk_io='default'
> pseudo_dir='/home/cantele/WORK/CODES/Quantum-ESPRESSO/pseudo'
> tefield=.true.
> dipfield=.true.
> /
> &SYSTEM
> ibrav=1
> celldm(1) = 20
> nat=3
> ntyp=2
> ecutwfc=30.0
> ecutrho=180.0
> occupations='smearing'
> degauss=0.01
> edir=3
> eamp=0.D0
> eopreg=0.1
> emaxpos=0.5
> /
> &ELECTRONS
> /
> ATOMIC_SPECIES
> O 15.9994 O.pbe-rrkjus.UPF
> H 1.00794 H.pbe-rrkjus.UPF
> ATOMIC_POSITIONS { Angstrom }
> O 0.0 0.0 0.0
> H 0.77 0.0 0.62
> H -0.77 0.0 0.62
> K_POINTS { gamma }
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>
--
------------------------------------------------------------------
Research Fellow,
Dept. of Physics, National Univ. of Singapore
10 Kent Ridge Crescent, Singapore, 119260
Tel: +65 6516 7844
------------------------------------------------------------------
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.democritos.it/pipermail/pw_forum/attachments/20090309/89d6df84/attachment.htm
More information about the Pw_forum
mailing list