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<p><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Dear </span><span style="caret-color: rgb(33, 33, 33); color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif; font-size: 12pt;">Mohaddeseh,</span></p>
<p><span style="caret-color: rgb(33, 33, 33); color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 15px;"><br>
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<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">> </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">1. In the NiO examples in the HP folder, there are two Ni
atoms, namely NI1 and Ni2. Fortunately, hubbard parameters are obtained the same for both. But for my structure Ti1 and Ti2 and Ti3 have different u values. </span></div>
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<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">If you obtain different U values for Ti1, Ti2, and </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Ti3, then
these species are inequivalent and this is OK</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">. If they were equivalent, you would obtain same U for all of them like in the example for NiO.</span></div>
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<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">> </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">in all of the literature just one U is reported for the metallic
element. Is it OK to report 3 different U values by linear response method or not?</span></div>
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<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">I presume that in the literature, empirical U was used - in this case it is hard (or maybe even </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">impossible)
to find different U for different inequivalent species. But with ab initio methods this comes out naturally from the linear </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">response of the system</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">.
And yes, it is </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">OK to report 3 different U, provided that you are sure that this is correct (i.e. </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">that
you indeed have three inequivalent species</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">) and that you explain in your paper </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">that
you computed U from first principles that allows you to have site-depend U. </span></div>
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<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">You might be interested checking these references about site-dependent U</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">:</span></div>
<div style="caret-color: rgb(33, 33, 33); color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 15px;">
<h5 class="authors" style="box-sizing: border-box; margin: 0.2rem 0px 2px; padding: 0px; color: rgb(85, 85, 85); font-family: "Proxima Nova", "Helvetica Neue", Helvetica, Helvetica, Arial, sans-serif; font-weight: 400; line-height: 1; text-rendering: optimizeLegibility; font-size: 1.14286rem;">
<span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">- </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">C. Ricca, I. Timrov, M. Cococcioni, N. Marzari, and U. Aschauer, </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Phys.
Rev. B</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);"> </span><span style="font-size: 12pt; box-sizing: border-box; font-weight: 700; line-height: inherit; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">99</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">,
094102 (2019).</span></h5>
<div><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">- </span><span style="color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif; font-size: 12pt;">C. Ricca, I. Timrov, M. Cococcioni, N. Marzari, and U.
Aschauer, </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Phys. Rev. Research </span><span style="box-sizing: border-box; font-weight: 700; line-height: inherit; font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">2</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">,
023313 (2020).</span></div>
<br>
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<p><span style="caret-color: rgb(33, 33, 33); color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 15px;"><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">> </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">2.
Is it necessary to relax the structure before starting the calculation of U parameters by linear response? In fact, the obtained U values from relax calculation and without relaxation are totally different with each other.</span></span><span style="caret-color: rgb(33, 33, 33); color: rgb(33, 33, 33); font-family: wf_segoe-ui_normal, "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif, serif, EmojiFont; font-size: 15px;"><br>
</span></p>
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<p><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">It depends what you want to do. U can be computed in two ways: 1) "one-shot", or 2) self-consistently. In the first case, one computes U for a given geometry and
that's it. In the second case, U is computed for a given geometry, then vc-relax is done using DFT+U (with U computed in the first step), then U is recomputed from the new geometry, and so on until both </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">the
geometry and U do not change (within specified thresholds). In general, the second option should be used. But if you want to compute U for a fixed geometry for some reason (e.g. for the experimental geometry, like here: I. Timrov et al., </span><span style="color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif; font-size: 12pt;">Phys.
Rev. Research </span><span style="color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif; font-size: 12pt; box-sizing: border-box; font-weight: 700; line-height: inherit;">2</span><span style="color: rgb(0, 0, 0); font-family: Arial, Helvetica, sans-serif; font-size: 12pt;">,
033265 (2020)</span><span style="font-size: 12pt;"><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">), then use the first option. If you want to read more about this, check two references above (C. Ricca et al.</span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">) </span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">and
this one: M. Cococcioni and N. Marzari, </span></span><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif;">Phys. Rev. Materials </span><span style="box-sizing: border-box; font-weight: 700; line-height: inherit; font-size: 12pt; font-family: Arial, Helvetica, sans-serif;">3</span><font face="Arial, Helvetica, sans-serif" size="3">,
033801 (2019). Last, we are preparing a manuscript with detailed explanations about the </font><font face="Arial, Helvetica, sans-serif">self-consistent calculation of Hubbard parameters.</font></p>
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<div><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Cheers,</span></div>
<div><span style="font-size: 12pt; font-family: Arial, Helvetica, sans-serif; color: rgb(0, 0, 0);">Iurii</span></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 Mohad Abbasnejad <mohaddeseh.abbasnejad@gmail.com><br>
<b>Sent:</b> Friday, August 28, 2020 5:32:46 PM<br>
<b>To:</b> Quantum ESPRESSO users Forum<br>
<b>Subject:</b> [QE-users] Regarding input file for hp.x</font>
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<div>Hello QE users<br>
</div>
There are two basic questions for preparing input files for hp.x<br>
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1. In the NiO examples in the HP folder, there are two Ni atoms, namely NI1 and Ni2. Fortunately, hubbard parameters are obtained the same for both. But for my structure Ti1 and Ti2 and Ti3 have different u values. in all of the literature just one U is reported
for the metallic element. Is it OK to report 3 different U values by linear response method or not?<br>
<br>
</div>
2. Is it necessary to relax the structure before starting the calculation of U parameters by linear response? In fact, the obtained U values from relax calculation and without relaxation are totally different with each other.<br>
<br>
</div>
<div>Any help would be appreciated.<br>
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<div>Regards,<br>
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<div>Mohaddeseh<br>
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<div>--<br>
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Mohaddeseh Abbasnejad, <br>
Assistant Professor of Physics,<br>
Faculty of Physics, <br>
Shahid Bahonar University of Kerman,<br>
Kerman, Iran<br>
P.O. Box 76169-133<br>
Tel: +98 34 31322199<br>
Fax: +98 34 33257434<br>
Cellphone: +98 917 731 7514<br>
E-Mail: <a href="mailto:mohaddeseh.abbasnejad@gmail.com" target="_blank">mohaddeseh.abbasnejad@gmail.com</a><br>
Website: <a href="http://academicstaff.uk.ac.ir/moabbasnejad" target="_blank">academicstaff.uk.ac.ir/moabbasnejad</a>
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