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<div class="moz-cite-prefix">On 6/15/23 21:12, Elio Physics wrote:<br>
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Dear professor Paulatto,</div>
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Thanks for the information. <br>
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1)Would that divergence produce negative line widths? I have
been trying to obtain some decent results for graphene but when
the smearing is above 1.0 , the code crashes stating that the
linewidth is negative! i tried to increase the grid dimension
but in vain.<br>
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<p>To get a negative linewidth it takes a seriously broken
calculation, as the last therm can mathematically be negative</p>
<p><img src="cid:part1.KFZ5q240.nA6oCBjt@cnrs.fr" alt=""></p>
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<p>But that would require that the population of the higher phonon
(q'') is higher than the lower phonon (q') as w'' = w+w' > w'.</p>
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<p>Also a broken compilation of the code, or a bug, but to say
anything I would need a specific case to test and reproduce.<br>
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2) Is there a flag in the input that ensures regularization or
one that imposes a cutoff?</div>
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<p>No, it has been done ad-hoc for the specific paper about 2D
systems, although I did not do those calculations, I'm not sure of
the details. It is very easily done in post-processing, if
store_lw=.true. is used to save the linewidths to file, using the
matlab script recompute_sma.m, or any home-made script. A bit more
complicated in the exact minimization method, setting a reasonable
Casimir scattering length may be the best bet. Exact algorithm is
very expensive to converge anyway, because one cannot use shifted
grid (and symmetry is not exploited at the moment)<br>
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Thank you <br>
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<div id="divRplyFwdMsg" dir="ltr"><font style="font-size:11pt"
face="Calibri, sans-serif" color="#000000"><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
Lorenzo Paulatto <a class="moz-txt-link-rfc2396E" href="mailto:lorenzo.paulatto@cnrs.fr"><lorenzo.paulatto@cnrs.fr></a><br>
<b>Sent:</b> Thursday, June 15, 2023 5:02 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum
<a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a><br>
<b>Subject:</b> Re: [QE-users] A question on the volume_factor
flag in d3_tk.x</font>
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<div dir="auto">Hello Elio,<br>
The problem is that tk is given for bulk per unit of volume.
When you do a 2D material in plane waves, you need to put a
lot of vacuum. The volume factor is used to make the value
independent on the amount of vacuum. It can is the ratio of
the bulk uni cell to the 2d unit cell, or the ratio between
the c axis in bulk and in the film, it is the same thing.<br>
<br>
Please not that 2d materials are very tricky: the thermal
conductivity from the quadratic band is integrable but
diverging. Using some kind of regularization or a cutoff may
be required.<br>
<br>
Cheets<br>
<br>
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<div dir="auto">On June 15, 2023 8:48:16 p.m. GMT+02:00, Elio
Physics <a class="moz-txt-link-rfc2396E" href="mailto:Elio-Physics@live.com"><Elio-Physics@live.com></a> wrote:</div>
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<span class="x_x_elementToProof x_ContentPasted0"
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font-size:12pt; color:rgb(0,0,0)">Dear all (and
specifically Professor Paulatto),</span>
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Sorry to bother you again with another question
regarding the d3q code. To calculate the lattice thermal
conductivity for 2D materials, we need to define a
volume_factor =H/V. H is defined as the interlayer
distance for the corresponding bulk material. If I
understood correctly, let us say we have a 1H MoS2, we
know that the bulk can be modeled as two layers (a
total of six atoms per unit cell). H would then be the
distance between the upper S layer of the bottom MoS2
and the lower S layer of the MoS2 on top. Correct?</div>
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<div class="x_x_elementToProof"><span
class="x_ContentPasted0">Now what if we have a 1T 2D
structure. Up to my knowledge, the bulk is modeled as
one layer ( 3 atoms per unit cell). In this case,
what would H be ? The thickness of the structure?</span></div>
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Regards</div>
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Elie Moujaes</div>
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Federal University of Rondonia</div>
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Brazil</div>
<span class="x_x_elementToProof x_ContentPasted0"
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font-size:12pt; color:rgb(0,0,0)">Porto Velho</span><br>
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<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
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