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Dear Robert,</div>
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Please have a look at this paper: <a href="https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.045141" id="LPlnk855446">
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.103.045141</a></div>
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Yes, generally, one should also redo the vc-relax calculations using updated U and V values using DFT+U+V. But if, for example, one wants to work with the fixed geometry (e.g. the experimental one), then obviously there is no need to do the vc-relax calculations.</div>
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Greetings,</div>
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Iurii</div>
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Dr. Iurii TIMROV</div>
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Tenure-track scientist</div>
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Laboratory for Materials Simulations (LMS)</div>
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Paul Scherrer Institut (PSI)</div>
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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 ROBERT MIKHAIL GUZMAN ARELLANO via users <users@lists.quantum-espresso.org><br>
<b>Sent:</b> Thursday, September 26, 2024 17:34<br>
<b>To:</b> users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
<b>Subject:</b> [QE-users] It is neccesary to make a vc-relax in each DFT U+V calculation?</font>
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<div dir="ltr">Dear members,
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<p>I am starting to work in DFT U+V making calculations with pw.x and hp.x of Quantum Espresso package. So my question is:</p>
<p>In order to calculate the U and V values with hp.x. What is the path to follow?</p>
<p>At his time. I am doing these steps.</p>
<p>0. Calibrate pseudo potentials, k-points, and frequency of waves and density. <br>
</p>
<p>1. Calculate the crystalline structure using vc-relax.</p>
<p>2. Make a scf calculation using the best atomic positions and unit cell parameters obtained in vc-relax calculation. In this calculation, I put a small value of U and V between orbitals. (1.d-3 eV)</p>
<p>3 run hp.x in order to calculate better values of U and V.</p>
<p>4 extract the U and V values calculated by hp.x, and put these in a new scf calculation and run the last.</p>
<p>5 repeat the 3 step and after the 4 step until the U and V values between 2 different calculations look equal or with small difference (0.01eV).</p>
<p>My Question is: is it necessary to make a vc-relax between the 3 and 4 steps? I looked at some examples which do that in order to calculate U value,but do not do the same when calculating V (interaction between different orbitals).<br>
</p>
<p>During this month I have been working with atoms whose valence orbitals are S and P, and I understand that for these orbitals, not being very localized like the D orbitals, it is necessary to work with U and V, where V responds to the coulomb interaction
between orbitals of neighboring atoms.<br>
</p>
<p>Thank's for your attention.</p>
<p>Best regards.</p>
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