Dear Giovanni,<br><br>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.<br>
<br>Best regards<br><br>Aihua<br><br><div class="gmail_quote">On Mon, Mar 9, 2009 at 10:19 PM, Giovanni Cantele <span dir="ltr"><<a href="mailto:Giovanni.Cantele@na.infn.it" target="_blank">Giovanni.Cantele@na.infn.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div>Aihua Zhang wrote:<br>
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Dear all,<br>
<br>
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<br>
<br>
lelfield = .true.<br>
efield = 0.01<br>
<br>
In the output file, it reports<br>
<br>
Electronic Dipole per cell (a.u.) -1.921145549061207<br>
Ionic Dipole per cell (a.u.) 116.1997104738884<br>
<br>
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!!<br>
<br>
Zhang<br>
<br>
<br>
</blockquote></div>
Hi,<br>
<br>
I'm not very expert about this, however I tried to reproduce your job. I got:<br>
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<br>
<br>
As far as I understand total dipole moment = 0.73268 a.u. = 0.73268 * 25.417463 / 10 Debye = 1.86 Debye.<br>
<br>
I remember I found strange results in electric field calculations some time ago, and the problem was where the<br>
molecule is placed within the unit cell, but I'm not very sure (that was a couple of years ago!).<br>
The input I used is in attachment.<br>
<br>
Giovanni<br>
<br>
<br>
-- <br>
<br>
<br>
<br>
Dr. Giovanni Cantele<br>
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche<br>
Universita' di Napoli "Federico II"<br>
Complesso Universitario di Monte S. Angelo - Ed. 6<br>
Via Cintia, I-80126, Napoli, Italy<br>
Phone: +39 081 676910<br>
Fax: +39 081 676346<br>
E-mail: <a href="mailto:giovanni.cantele@cnr.it" target="_blank">giovanni.cantele@cnr.it</a><br><font color="#888888">
<a href="mailto:giovanni.cantele@na.infn.it" target="_blank">giovanni.cantele@na.infn.it</a><br>
Web: <a href="http://people.na.infn.it/%7Ecantele" target="_blank">http://people.na.infn.it/~cantele</a><br>
Research Group: <a href="http://www.nanomat.unina.it" target="_blank">http://www.nanomat.unina.it</a><br>
<br>
</font><br> &CONTROL<br>
calculation='scf'<br>
title='H2Otest'<br>
verbosity='high'<br>
restart_mode='from_scratch'<br>
nstep=100<br>
iprint=1<br>
tprnfor=.true.<br>
outdir='./tmp/'<br>
prefix='H2Otest'<br>
disk_io='default'<br>
pseudo_dir='/home/cantele/WORK/CODES/Quantum-ESPRESSO/pseudo'<br>
tefield=.true.<br>
dipfield=.true.<br>
/<br>
&SYSTEM<br>
ibrav=1<br>
celldm(1) = 20<br>
nat=3<br>
ntyp=2<br>
ecutwfc=30.0<br>
ecutrho=180.0<br>
occupations='smearing'<br>
degauss=0.01<br>
edir=3<br>
eamp=0.D0<br>
eopreg=0.1<br>
emaxpos=0.5<br>
/<br>
&ELECTRONS<br>
/<br>
ATOMIC_SPECIES<br>
O 15.9994 O.pbe-rrkjus.UPF<br>
H 1.00794 H.pbe-rrkjus.UPF<br>
ATOMIC_POSITIONS { Angstrom }<br>
O 0.0 0.0 0.0<br>
H 0.77 0.0 0.62<br>
H -0.77 0.0 0.62<br>
K_POINTS { gamma }<br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>------------------------------------------------------------------<br>Research Fellow,<br>Dept. of Physics, National Univ. of Singapore<br>10 Kent Ridge Crescent, Singapore, 119260<br>
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