Hi Prof. Gironcoli,<br><br>Thank you for your fast reply. I tried the following calculation. It gives me<br> ! total energy = -325.65235136 Ry. <br>But Some of rho values are negative when I do post processing. What could be the possible reason?<br>
<br> &control<br> calculation = 'scf'<br> restart_mode='from_scratch',<br> prefix='Ge',<br> pseudo_dir = '$PSEUDO_DIR/',<br> outdir='$TMP_DIR/'<br> &system<br>
ibrav= 0,<br> nat= 2, ntyp= 2,<br> occupations = 'smearing',smearing='marzari-vanderbilt',<br> degauss=0.05,<br> nosym=.true.,<br> ecutwfc = 110<br> ecutrho = 880<br> tot_charge = +3,<br>
assume_isolated=.true.<br> /<br> &electrons<br> diagonalization = 'david',<br> mixing_mode = 'plain',<br> mixing_beta = 0.7<br> conv_thr = 1.0d-7<br> electron_maxstep=200<br> /<br><br>
CELL_PARAMETERS cubic<br> 40.0 0.0 0.0<br> 0.0 40.0 0.0<br> 0.0 0.0 40.0<br>ATOMIC_SPECIES<br> Ge1 72.61 Ge.pbe-paw_kj.UPF<br> Ge2 72.61 Ge.pbe-paw_kj.UPF<br>ATOMIC_POSITIONS<br> Ge1 0.50 0.50 0.50 0 0 0<br> Ge2 0.5 0.50 0.70 0 0 0 0<br>
<br>K_POINTS {automatic}<br> 1 1 1 0 0 0<br><br>Thanks and Best Regards,<br>Baowei Liu<br><br><div class="gmail_quote">On Sat, Oct 2, 2010 at 9:58 AM, Stefano de Gironcoli <span dir="ltr"><<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">the code can perform calculation for charged system using the variable<br>
tot_charge.<br>
By default the code performs the calculation for a periodic system<br>
(adding a compensating background to eliminate the G=0 divergence).<br>
In the limit of large cells this eventually converge to the isolated case.<br>
There are various techniques to perform calculations for isolated<br>
systems with smaller cells.<br>
Read carefully the description of assume_isolated variable in the system<br>
namelist<br>
best,<br>
<br>
Stefano de Gironcoli - SISSA and DEMOCRITOS<br>
<div><div></div><div class="h5"><br>
Baowei Liu wrote:<br>
> Dear all members,<br>
><br>
> I am trying to calculate the potential between two ions, -- A(+2) and A(+1)<br>
> for example. When the two ions are far away from each other, there's only<br>
> Coulumb potential. But when the two ions are close enough, the electron<br>
> distribution will be important for the potential. Can QE be used to<br>
> calculate the energy or charge density for a system of two charged<br>
> particles? It will be great if QE can give the energy for different<br>
> distances. Just setting the tot_charge (=+3 in this example) is kind of not<br>
> what I want.<br>
> Thanks in advance.<br>
><br>
> Baowei Liu<br>
><br>
><br>
</div></div>> ------------------------------------------------------------------------<br>
><br>
> _______________________________________________<br>
> Pw_forum mailing list<br>
> <a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
> <a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>
><br>
<br>
_______________________________________________<br>
Pw_forum mailing list<br>
<a href="mailto:Pw_forum@pwscf.org">Pw_forum@pwscf.org</a><br>
<a href="http://www.democritos.it/mailman/listinfo/pw_forum" target="_blank">http://www.democritos.it/mailman/listinfo/pw_forum</a><br>
</blockquote></div><br>