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<p>Dear M. Inukai,</p>
<p><br>
</p>
<p>I would like to add a small note to the very comprehensive
response of Iurii and Oscar regarding the "pseudo_hermitian"
option:</p>
<p><br>
</p>
<p>In my experience if the code fails with this option set to .TRUE.
it might mean that there are some problems with your system or
parameters ( i.e. too low kinetic energy cutoff with respect to
the amount of Lanczos recursion iterations you want). </p>
<p><br>
</p>
<p>Best regards,</p>
<p>Oleksandr Motornyi<br>
</p>
<br>
<div class="moz-cite-prefix">On 12/03/2018 11:11 AM, Timrov Iurii
wrote:<br>
</div>
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<div>Dear M. Inukai,</div>
<div><br>
1. num_eign = number of eigenstates (excitations) which will
be<br>
computed. This parameter must be chosen based on how large
energy range<br>
for the spectrum the user is interested in. The bigger the
energy range,<br>
the larger num_eign is. A priori it is not possible to guess
this<br>
number, because it depends on the system. Try with some
reasonable<br>
numbers (say, 5, 10, or 15) and then check whether this is
enough to<br>
obtain a converged spectrum in the energy range of interest.<br>
<br>
2. 'num_basis_max' is the maximum number of basis allowed in
the subspace.<br>
In every Davidson iteration the number of basis used in the
subspace is increased</div>
<div>by num_init. When num_basis_max is reached, a discharging<br>
routine is called (this variable determines the memory
requirement). The <br>
larger the parameter num_eign, the larger num_basis_max
would be needed.<br>
Try with some reasonable numbers, run test calculations, and
then<br>
increase/decrease num_basis_max based on your observations.
Use examples<br>
in TDDFPT to get an idea about typical values of this
parameter.<br>
<br>
3. 'ecutfock' is the kinetic energy cutoff (Ry) for the
exact exchange operator<br>
in the exact-exchange (EXX) type calculations. The meaning
of this parameter <br>
</div>
<div>is the same as in the PW code (pw.x), hence see the
documentation in PW/Doc.
<br>
</div>
<div>The value of ecutfock cannot be smaller than ecutwfc.<br>
<br>
4. 'itermax0' generally you can use the same number that you
computed<br>
with turbo_laczos (itermax).<br>
<br>
5. 'p_nbnd_occ and p_nbnd_virt' if you are interested only
in energy and<br>
absorption spectrum, it is not necessary to use all occupied
and virtual<br>
orbitals. Using all states is useful only if you are
interested in the<br>
interpretation of the eigenstates.<br>
<br>
6. 'pseudo_hermitian' When you use .FALSE., the code will be
2 times<br>
slower but the result must be the same. So it is always
recommended to<br>
use .TRUE. unless it does not work for some reasons. The
.FALSE. option<br>
was implemented first, and hence it is still kept in the
code for the<br>
case when .TRUE. does not work.<br>
<br>
7. 'CH4-BOND' this is obsolete and will be removed in the
next release of QE. <br>
</div>
<div>The meaning of "project", "absorbtive", and "dispersive"
is not documented,</div>
<div>it was introduced by Osman Baris Malcioglu around ~2011
(CPC 182, 1744 (2011)).
<br>
</div>
<div>These parameters are related to the calculation of the
response charge density.
<br>
</div>
<div>You may try either to understand what does these keywords
mean by looking into the code or</div>
<div>try to contact Baris and ask him directly.<br>
</div>
<div><br>
Best regards,<br>
Oscar Baseggio - postdoctoral researcher, SISSA, Trieste,
Italy</div>
<div>Iurii Timrov - postdoctoral researcher, EPFL STI IMX
THEOS, Lausanne, Switzerland<br>
</div>
<br>
</div>
<hr tabindex="-1" style="display:inline-block; width:98%">
<div id="x_divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
color="#000000" face="Calibri, sans-serif"><b>From:</b>
users <a class="moz-txt-link-rfc2396E" href="mailto:users-bounces@lists.quantum-espresso.org"><users-bounces@lists.quantum-espresso.org></a> on
behalf of 犬飼 学 <a class="moz-txt-link-rfc2396E" href="mailto:inukai.manabu@nitech.ac.jp"><inukai.manabu@nitech.ac.jp></a><br>
<b>Sent:</b> Monday, November 26, 2018 2:17:37 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a><br>
<b>Subject:</b> [QE-users] How to decide value of TDDFPT
variables</font>
<div> </div>
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<font size="2"><span style="font-size:10pt;">
<div class="PlainText">Dear developers<br>
<br>
Although I have red *.html in Doc (TDDFPT), <br>
I do not understand same variables in detail. <br>
<br>
Would you tell me any advices ?<br>
----------<br>
How do I decide 'num_eign', 'num_basis_max' and 'ecutfock'
in *.dav-in ?<br>
<br>
How do I decide 'itermax0' in *.tddfpt_pp-in ?<br>
<br>
I set number of eigenvalue (<= EF) to p_nbnd_occ and<br>
set number of eigenvalue (>= EF) to p_nbnd_virt ?<br>
Is it best ?<br>
<br>
What do absorbtive and dispersive mean in CH4-BOND ?<br>
<br>
What does 'project' mean in CH4-BOND ?<br>
<br>
When do I use pseudo_hermitian=.false.<br>
--------<br>
Best Regards,<br>
M. Inukai<br>
<br>
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<br>
<pre class="moz-signature" cols="72">--
Oleksandr Motornyi
PhD candidate
Laboratoire des Solides Irradies
Ecole Polytechnique (Palaiseau, France)</pre>
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