<div dir="ltr"><div dir="ltr"><div>Hello, Lorenzo,</div><div><br></div><div>From the user guide of phonon, here is the introduction of matdyn.x: <br></div><div><br></div><div>PH/matdyn.x: produces phonon frequencies at a generic wave vector using the IFC file<br>calculated by q2r.x; may also calculate phonon DOS, the electron-phonon coefficient λ,<br>the function α2 F (ω). And I do have a output file of lambda, is it because the latest version of matdyn.x that can do the calculation of lambda ?</div><div><br></div><div>This is just referred from<span class="gmail-repo-root gmail-js-repo-root"><span class="gmail-js-path-segment"><span>quantum-espresso</span></span></span><span class="gmail-separator">/</span><span class="gmail-js-path-segment"><span>PHonon</span></span><span class="gmail-separator">/</span><span class="gmail-js-path-segment"><span>examples</span></span><span class="gmail-separator">/</span><span class="gmail-js-path-segment"><span>example03</span></span><span class="gmail-separator">/</span><strong class="gmail-final-path">run_example</strong>
</div><div><br></div><div>Best <br></div><div><br></div><div>Chao Lei<br></div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr">On Mon, 29 Oct 2018 at 03:52, Lorenzo Paulatto <<a href="mailto:paulatz@gmail.com">paulatz@gmail.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Matdyn just interpolates the 2-body force constants to get the dynamical <br>
matrix at an arbitrary q point and diagonalizes it. It does not care if <br>
the frequencies are positive or negative, it also does not compute any <br>
electron-phonon coupling.<br>
<br>
kind regards<br>
<br>
On 23/10/2018 23:21, Chao Lei wrote:<br>
> Hello, Lorenzo,<br>
> <br>
> Thanks for your reply, I am using matdyn.x and it already got the lambda <br>
> vs broadening without NaN or mathematical errors, the negative frequency <br>
> makes sense for me. So in matdyn.x the code does not do any check on the <br>
> frequencies too ? or it just neglected the negative frequency when doing <br>
> the sum ?<br>
> <br>
> Best wishes<br>
> <br>
> Chao Lei<br>
> Pos-doc<br>
> The University of Texas at Austin<br>
> <br>
> On Tue, 16 Oct 2018 at 02:43, Lorenzo Paulatto <<a href="mailto:paulatz@gmail.com" target="_blank">paulatz@gmail.com</a> <br>
> <mailto:<a href="mailto:paulatz@gmail.com" target="_blank">paulatz@gmail.com</a>>> wrote:<br>
> <br>
> Hello Chao,<br>
> do you mean, if you can compute lambda, or you have computed it<br>
> already and you are asking if it makes sense?<br>
> THe big problem with negative frequencies with this kind of system<br>
> is that you cannot really impose conservation of energy, but as in<br>
> elph conservation of energy is maybe not crucial. Anyway, the<br>
> original lambda.x code does not do any check on the frequencies, so<br>
> you probably get NaN or mathematical errors if you try to use it.<br>
> <br>
> Lambda.f90 is a very simple code, I think you may try to edit it and<br>
> see if different recipes can give something reasonable (i.e. skip a<br>
> mode when w2 is negative, use a complex omega=sqrt(w2) but take<br>
> delta( |e-omega|)...), sum the contribution with a weight<br>
> exp(-IMAG(omega)/something),....<br>
> <br>
> Of course, playing with the code can help thinking, but does not<br>
> replace it.<br>
> <br>
> cheers<br>
> <br>
> On Mon, 15 Oct 2018 at 18:22, Chao Lei <<a href="mailto:leichao.forum@gmail.com" target="_blank">leichao.forum@gmail.com</a><br>
> <mailto:<a href="mailto:leichao.forum@gmail.com" target="_blank">leichao.forum@gmail.com</a>>> wrote:<br>
> <br>
> Dear users,<br>
> <br>
> I am calculating electron-phonon using ph.x, which got negative<br>
> frequency. This is OK for me as it is expected, however, I have<br>
> a question that how does ph.x treat the negative frequency when<br>
> use them to calculate the electron-phonon coupling constant<br>
> lambda ? Thanks for your reply<br>
> if you know the answer.<br>
> <br>
> Best<br>
> <br>
> Chao Lei<br>
> Pos-doc<br>
> The University of Texas at Austin<br>
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> <br>
> <br>
> -- <br>
> Lorenzo Paulatto - Paris<br>
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<br>
-- <br>
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