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<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Dear Wei Zhang, <br /> <br /> first of all, I would like to recall that it would be appreciated</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">if you specify your name and affiliation when sending e-mails to</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">the forum mailing list (I didn't spot it in your message). <br /> <br /> Coming to your point:<br /> <br /> 1. In the file matdyn.modes you find the <span style="text-decoration: underline;">eigenmodes</span>, obtained from <br /> the eigenvectors of the dynamical matrix in the following way: <br /> <br /> d (s,alpha) = u (s,alpha) / sqrt(amass(s)), <br /> <br /> where: s labels the atoms in the unit cell, alpha is the cartesian <br /> index, u is the eigenvector of the dynamical matrix, d is the eigenmode,</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">amass(s) is the mass of the s-th atom. <br /> The eigenmodes are then <span style="text-decoration: underline;">normalized</span> and written to file, so what you </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">read in the file matdyn.modes is:</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">d' = d / sqrt(|d|^2)</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">2. The routine you refer to (WRITE_EIGENVECTORS.F90), in particular the </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">lines you reported, is intended to write the <span style="text-decoration: underline;">eigenvectors</span> of the</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">dynamical matrix, not the eigenmodes.</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">The routine which writes the <span style="text-decoration: underline;">eigenmodes</span> is writemodes (you find it</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">inside WRITE_EIGENVECTORS.F90, below the lines you refer to).</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">So, before using the information contained in the output files, please</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">be sure to know if you are reading (or if you are interested to) the</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">eigenmodes rather than the eigenvectors of the dynamical matrix.</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">3. About the units: in all the cases the vectors printed are normalized,</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">so they are dimensionless (since they are obtained by dividing the</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">vector by its magnitude, both quantities having the same dimensions).</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">To get a dimensioned quantity you should multiply the vector by a</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">constant (that I will call amplitude from now on). The amplitude has</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">the dimension of a length (Angstrom, bohr radii, m, cm, depending on</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">which units you want to use) and defines the "total length" (or magnitude)</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">of the vector (which, otherwise, without being multiplied by the</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">amplitude would have magnitude 1).</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Note: in order to do "frozen phonon calculations" the <span style="text-decoration: underline;">eigenmodes should </span></div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"><span style="text-decoration: underline;">be used</span>, not the eigenvectors. <br /> <br /> I hope this helps, Best regards,</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">Andrea Urru</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">PhD student in Condensed Matter</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">SISSA Via Bonomea 265</div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace">34136 Trieste (TS)<br /> </div>
<div class="pre" style="margin: 0; padding: 0; font-family: monospace"> </div>
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<div class="pre" style="margin: 0; padding: 0; font-family: monospace"><br /> On 2020-01-30 07:08, Wei Zhang wrote:
<blockquote type="cite" style="padding: 0 0.4em; border-left: #1010ff 2px solid; margin: 0">BLOCKQUOTE{margin-Top: 0px; margin-Bottom: 0px; margin-Left: 2em}<br /> body {border-width:0;margin:0} img {border:0;margin:0;padding:0} <br /> Dear all, <br /> I am not sure about the acuurate unit of phonon eigenvectors printed<br /> at the MATDYN.MODES. e.g. , <br /> <br /> In<br /> <a href="https://www.mail-archive.com/users@lists.quantum-espresso.org/msg04000.html" target="_blank" rel="noreferrer">https://www.mail-archive.com/users@lists.quantum-espresso.org/msg04000.html</a><br /> <br /> The authors mentioned : the units is masses^(-1/2) (masses are in<br /> atomic rydberg units, i.e. sqrt(-911.444*amass(1) or (2) ......) ). <br /> <br /> In WRITE_EIGENVECTORS.F90 OF QE, it writes <br /> z_((na-1)*3+ipol,i) = z((na-1)*3+ipol,i) * SQRT(AMU_RY*AMASS(NTA)) <br /> which has already been MULTIPLIED by sqrt(amu_ry*amass(nta)) , i.e.,<br /> sqrt(-911.444*amass(1) or (2) ......) ?? (As I have not found the<br /> value of constant AMU_RY used in QE ) <br /> <br /> The sum of the norm of XYZ of every modes in matdyn.modes equals to 1,<br /> which has been normalized, So I want to check that: the real<br /> displacement of XYZ should be divided by sqrt(911.444*amass(1) or (2)<br /> ......) with Bohr length unit? <br /> <br /> Thanks! <br /> <br /> 2020-01-30 <br /> -------------------------<br /> body {font-size:10.5pt; font-family:微软雅黑,serif}<br /> _______________________________________________<br /> Quantum ESPRESSO is supported by MaX (<a href="http://www.max-centre.eu/quantum-espresso" target="_blank" rel="noreferrer">www.max-centre.eu/quantum-espresso</a>)<br /> users mailing list <a href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a><br /> <a href="https://lists.quantum-espresso.org/mailman/listinfo/users" target="_blank" rel="noreferrer">https://lists.quantum-espresso.org/mailman/listinfo/users</a></blockquote>
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