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<p>Dear Vivek,</p>
<p><br>
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<p>If your supercell is large enough, you can try to compute the absorption spectrum using the turbo_lanczos.x or turbo_davidson.x codes and using only one k point (k=0). For these codes you need to specify "<span>K_POINTS {gamma}</span>". k point grids different
from k=0 are currently not supported by these codes.</p>
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</p>
<p>If you do need to use k point grids, then yes you can try to use the turbo_eels.x code as a workaround (though originally this code was developed to model EELS spectra). Then you need to plot Im(eps), where eps is the dielectric function. For optical absorption,
the transferred momentum is vanishing (q->0), so you can specify some small numbers for q1, q2, q3 (but not exactly zero, because this limit is not implemented). So you can try something like (note, the direction of q is not important):</p>
<p></p>
<div> q1 = 0.001,<br>
q2 = 0.000,<br>
q3 = 0.000</div>
<br>
<p></p>
<p>Cheers,</p>
<p>Iurii<br>
</p>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Vivek Christhunathan <vivekppn@gmail.com><br>
<b>Sent:</b> Tuesday, August 18, 2020 4:19:52 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum<br>
<b>Subject:</b> [QE-users] q1, q2, q3 values for turbo_eels.x method</font>
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<div class="gmail_default">Hi Everyone,</div>
<div class="gmail_default"><br>
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<div class="gmail_default">Greetings!!!</div>
<div class="gmail_default"><br>
</div>
<div class="gmail_default">I am trying to do absorption spectrum calculation for anatase TiO2 which consist of 48 atoms (2x2x1 supercell) by using turbo_eels.x method. I have done scf calculation for this. </div>
<div class="gmail_default">The default value for q1, q2, and q3 is 1. So, to get the correct output data for the calculation what value should I give for q1, q2, and q3 tags which are present in the turbo_eels.x. </div>
<div class="gmail_default"><span style="background-color:transparent"><span class="gmail_default"><br>
</span></span></div>
<div class="gmail_default"><span style="background-color:transparent"><span class="gmail_default">Please find the attached files for the reference.</span></span><span class="gmail_default" style="background-color:transparent;font-size:16px"></span><span style="background-color:transparent;font-family:Arial,Helvetica,sans-serif"><font face="verdana, sans-serif" style="font-size:16px"></font><span class="gmail_default" style="font-size:16px;font-family:verdana,sans-serif"> </span></span><br>
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<div style="background-color:transparent;margin-top:0px;margin-bottom:0px"><span style="background-color:transparent"><span class="gmail_default"><font face="verdana, sans-serif">Your response is highly appreciated. </font></span></span></div>
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<div style="background-color:transparent;margin-top:0px;margin-bottom:0px"><span style="background-color:transparent"><span class="gmail_default"><font face="verdana, sans-serif">Thanks in advance.</font></span></span></div>
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<div style="background-color:transparent;margin-top:0px;margin-bottom:0px"><font face="verdana, sans-serif"><span style="background-color:transparent;color:rgb(0,0,0)">Kind Regards,</span><br>
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<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">Vivek C</font></p>
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<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">__________________________________</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><font face="verdana, sans-serif">Vivek Christhunathan</font></p>
<p class="MsoNormal" align="left" style="color:rgb(0,0,0)"><span lang="EN-US"><font face="verdana, sans-serif">PhD researcher</font></span></p>
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