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Dear Sun,<br>
<br>
Thanks for your reply. I know this. Automatic k-mesh is only
used in the scf run. In the following <b>nscf </b>run I used a
self defined k-mesh, which can be seen in the attached file
fccAu.nscf4eps.in of the original mail.<br>
<br>
Best regards,<br>
Liu Gui-Bin<br>
<br>
于 2011/7/7 23:53, Tao Sun 写道:
<blockquote
cite="mid:CAEQ9wfAAJhdXbPTiLXWowbRioQ_N=Ssi6BVyOwiE73Unv8oLAA@mail.gmail.com"
type="cite">
<pre wrap="">Hi.
I have never done dielectric function calculations. But the kmesh you
are using "15 15 15 1 1 1" automatic seems to be inconsistent with
this manual. <a class="moz-txt-link-freetext" href="https://ir.library.dc-uoit.ca/bitstream/10155/159/3/McNelles_Phillip_appendixA.pdf">https://ir.library.dc-uoit.ca/bitstream/10155/159/3/McNelles_Phillip_appendixA.pdf</a>.
Maybe this is worth checking, i.e. set the full kmesh by hand,
without symmetry.
Best
Tao
On Thu, Jul 7, 2011 at 4:39 AM, gbliu <a class="moz-txt-link-rfc2396E" href="mailto:goodluck_1982@163.com"><goodluck_1982@163.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear all,
I want to calculate dielectric function of carbon nanotube, but I have
no experiences of calculating dielectric function before. Hence, I decide to
start with a simple case of fcc gold, because there are referable results
from wien2k (wien2k is capable of simple case such as fcc Au, but too
resource consumptive to deal with large cells such as CNT).
Because epsilon.x doesn't support USPP, the UPF file of Au is got by
converting fhi file from abinit using fhi2upf.x. I calculate fcc Au with
a=7.71bohr and 15x15x15 k-mesh using both pwscf(v4.3) and wien2k. First I
check the band structures and find that the results from both softwares
agree well (see attachments). But the results of epsilon from pwscf is not
satisfactory as the results from wien2k:
(1) Figures imag_eps and real_eps are the compares with only interband
contribution. (note that for pwscf, I subtract the intraband contribution
[-omega_p^2/omega^2] to get only interband contribution for compares). We
can see the differences are notable. What's the reason?<i><b> </b></i><font color="#ff0000"><u><b>BTW, I use a
homogeneous k-mesh also 15x15x15 generated by myself for epsilon calculation
(see input file fccAu.nscf4eps.in).</b></u></font>
------input for epsilon.x--------
&inputpp
outdir='./work'
prefix='fccAu'
calculation='eps'
/
&energy_grid
smeartype='gauss'
intersmear=0.1d0
intrasmear=0d0
wmax=20d0
wmin=0d0
nw=600
shift=0d0
/
--------------------------------
(2) As for the intraband contribution, wien2k gives the plasma frequency
9.0075eV which agrees well with experimental value (ref:
<a class="moz-txt-link-freetext" href="http://wave-scattering.com/drudefit.html">http://wave-scattering.com/drudefit.html</a>), but the result from epsilon.x is
puzzling.
Specifically, plasma frequency given in the output of epsilon.x is dependent
on the input parameters:
<1>. intrasmear=0, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
14.877926200
<2>. intrasmear=0, wmax=10d0 --> The bulk xx plasmon frequency [eV] is:
7.625822195
<3>. intrasmear=0, wmax=6d0 --> The bulk xx plasmon frequency [eV] is:
3.156554381
<4>. intrasmear=0.1, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
15.766403193
<5>. intrasmear=0.1, wmax=10d0 --> The bulk xx plasmon frequency [eV] is:
9.322251787
<6>. intrasmear=0.1, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
6.263713572
However, none of these values is the one got by fitting the results using
Drude model [ 1 - omega_p^2/(omega^2+i*omega*gamma), gamma is the intrasmear
here ]. By fitting the results using Drude model, I get omega_p=5.528769eV,
for all the cases above (<1>~<6>). But this omega_p is far from the
experimental value (~9 eV)! What's wrong? And what are the meanings of the
values given in <1>~<6> ?
How can I get more accurate results like the ones from wien2k?
Please help me if you know something about this, thanks in advance!
Best regards!
Liu Guibin
Postdoctoral Fellow,
Department of Physics,
The University of Hong Kong
<a class="moz-txt-link-abbreviated" href="mailto:gbliu@hku.hk">gbliu@hku.hk</a>
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</pre>
</blockquote>
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