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
