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<blockquote type="cite"
cite="mid:1072087897.10243806.1762356473531.JavaMail.zimbra@iitkgp.ac.in">
<pre wrap="" class="moz-quote-pre">More specifically, is it true that calculating Raman spectra for metals is not implemented in Quantum Espresso. </pre>
</blockquote>
<p>Hello,</p>
<p>the calculation of both dielectric matrix and Raman tensor in
phonon is only available for insulators and semiconductors, it
also lacks gradient correction and spin polarization. If you try
to fool the code by not using a smearing, you will get nonsensical
dielectric tensor, as you did. You can compute the
frequency-dependent epsilon with the code epsilon.x, this will
allow you to compute the Raman response for a given laser
frequency.</p>
<p>You can compute the Raman tensor of metals using finite
differentiation of the frequency-dependent dielectric tensor along
phonon displacement. This can easily be done by hand:<br>
1. take the displacements "v" of the phonon from the dynamical
matrix file (they are 3*n complex numbers, but at Gamma the
imaginary parts are zero)</p>
<p>2. move the atoms up and down this direction by a small amount
(i.e. ±1.d-3 bohr) </p>
<p>3. compute the dielectric tensor in both cases (using epsilon.x)</p>
<p>4. compute the derivative. (epsilon(r+h v)-epsilon(r-h v))/2h</p>
<p>This will give you the Raman tensor in cartesian axes for the
given phonon.</p>
<p><br>
</p>
<p>A more efficient alternative, is via the finite differentiation
of forces w.r.t an external electric field, as explained in
doi:10.1038/s41524-024-01236-3. The methodology should be
available via the Aiida interface.</p>
<p>kind regards</p>
<p><br>
</p>
<blockquote type="cite"
cite="mid:1072087897.10243806.1762356473531.JavaMail.zimbra@iitkgp.ac.in">
<pre wrap="" class="moz-quote-pre">How does that work in VASP (for metals)?</pre>
</blockquote>
<p>No idea, you should its developers.</p>
<p><br>
</p>
<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IR IMPMC - CNRS UMR 7590 / Sorbonne Université / MNHN <br>
phone: +33 (0)1 442 79822 / telegram: lpaulatto<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
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