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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 'CH4-BOND' this is obsolete and will be removed in the next release of QE.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>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of 犬飼 学 <inukai.manabu@nitech.ac.jp><br>
<b>Sent:</b> Monday, November 26, 2018 2:17:37 AM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> [QE-users] How to decide value of TDDFPT variables</font>
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<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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