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Dear Robert,</div>
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Originally, DFT+U and DFT+U+V were introduced to study transition-metal and rare-earth compounds. So usually, U has been applied to d and f electrons, and V for d-p and similar couples. </div>
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In your system, you have only s and p electrons. Now there are more and more studies where U and V are applied to these electronic states (see e.g.
<a href="https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.043410" id="LPlnk202270" class="OWAAutoLink">
https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.2.043410</a>). I do not have much experience in using DFT+U and DFT+U+V with U and V from linear response for these systems. But I know that ACBN0 is used quite extensively for these systems
and U and V are positive. </div>
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HTH</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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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> ROBERT MIKHAIL GUZMAN ARELLANO <rguzmana@unmsm.edu.pe><br>
<b>Sent:</b> Saturday, September 28, 2024 02:03<br>
<b>To:</b> Timrov Iurii <iurii.timrov@psi.ch><br>
<b>Cc:</b> users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
<b>Subject:</b> Re: [QE-users] It is neccesary to make a vc-relax in each DFT U+V calculation?</font>
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<div dir="ltr">Thanks a lot for your response.</div>
<div><br>
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<div>I was reading the paper that you recommended to me and I notice that your U and V values are positive.</div>
<div><br>
</div>
<div>I am practicing the DFT U + V in graphane (graphene -C- completely hydrogenated - 4 atoms in the unit cell) with the objective to calculate U and V values of carbon and hydrogen orbitals or between them. I used the protocol of your paper and I am considering
the HSE band structure calculation as a target, where the last gives a greater gap energy than the GGA DFT calculations.</div>
<div><br>
</div>
<div>I obtained positive U values but the V values are negatives.</div>
<div><br>
</div>
<div>These are:</div>
<div><br>
</div>
<div>ATOMIC_SPECIES<br>
C 12.0107 C.pbe-n-kjpaw_psl.1.0.0.UPF<br>
H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF<br>
ATOMIC_POSITIONS {angstrom}<br>
C 0.0000000000 0.0489411798 4.0736189551<br>
C 0.0000000000 1.5156118708 3.6147177498<br>
H 0.0000000000 0.0493473355 5.1835009290<br>
H 0.0000000000 1.5152618823 2.5048489230<br>
K_POINTS {automatic}<br>
12 12 1 0 0 0<br>
HUBBARD ortho-atomic<br>
V C-2P C-2P 1 1 2.8212<br>
V C-2P C-2P 2 2 2.8212<br>
<b>V C-2P H-1S 1 3 -0.0283<br>
V C-2P H-1S 2 4 -0.0283<br>
V C-2P C-2P 1 2 -0.1355</b><br>
V H-1S H-1S 3 3 4.3467<br>
V H-1S H-1S 4 4 4.3467<br>
</div>
<div><br>
</div>
<div>So I am wondering what is the criteria to validate or accept a negative V, and another question is which orbitals need to be selected for a V and U calculations. For example in the commented paper, the Mn-3d and O-2p orbitals are considered but avoided
the others valence orbitals. I am thinking that the most energetic orbitals of each atom must be considered... Could you recommend another work where discuss it ?</div>
<div><br>
</div>
<div>Thanks for the attention!!</div>
<div><br>
</div>
<div><br>
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<div dir="ltr" class="x_gmail_attr">El vie, 27 sept 2024 a las 3:01, Timrov Iurii (<<a href="mailto:iurii.timrov@psi.ch">iurii.timrov@psi.ch</a>>) escribió:<br>
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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="x_m_-2940545350976448284LPlnk855446" target="_blank">
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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CH-5232 Villigen, Switzerland</div>
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+41 56 310 62 14</div>
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<a href="https://www.psi.ch/en/lms/people/iurii-timrov" id="x_m_-2940545350976448284OWA02c45e06-4aa5-3176-da04-635eb55f8707" rel="noopener noreferrer" target="_blank">https://www.psi.ch/en/lms/people/iurii-timrov</a></div>
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<div id="x_m_-2940545350976448284divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <<a href="mailto:users-bounces@lists.quantum-espresso.org" target="_blank">users-bounces@lists.quantum-espresso.org</a>>
on behalf of ROBERT MIKHAIL GUZMAN ARELLANO via users <<a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a>><br>
<b>Sent:</b> Thursday, September 26, 2024 17:34<br>
<b>To:</b> <a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a> <<a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a>><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,
<div>
<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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