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<p class="MsoNormal">Dear Iurii,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Yes, to be more precise I mean that when I am looking at these systems, I am modelling them as being nonmagnetic and so I was wondering whether it was the spin degeneracy that was causing this difference.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I am typically looking at pressure-induced structural transitions in systems with complex magnetic ground states. However, in some cases the exact magnetic configurations are unknown and so to simplify the problem (and since these structural
transitions occur at high temperature in the paramagnetic state) I have been trying to perform the calculations in the nonmagnetic state. It is in these instances where I see this approximate doubling of U: i.e. when I allow the system to relax into a FM ordered
state (with nspin=2) before using hp.x the value of U ends up being around half that of when I don’t include spin effects (nspin=1).
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I hope this clarifies what I have been seeing.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best wishes,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Theo Weinberger<o:p></o:p></p>
<p class="MsoNormal">PhD Student<o:p></o:p></p>
<p class="MsoNormal">University of Cambridge<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><b><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:EN-GB">From:</span></b><span lang="EN-US" style="mso-ligatures:none;mso-fareast-language:EN-GB"> users <users-bounces@lists.quantum-espresso.org>
<b>On Behalf Of </b>Iurii Timrov via users<br>
<b>Sent:</b> Tuesday, September 12, 2023 10:31 AM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> Re: [QE-users] Spin counting in hp.x with paramagnetic metals<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p><span style="font-size:12.0pt;color:black">Dear Theo,<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p><span style="font-size:12.0pt;color:black">How do you model the paramagnetic state? Please note that "paramagnetic" and "nonmagnetic" state is not the same thing.
<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p><span style="font-size:12.0pt;color:black">For nonmagnetic calculations there is a factor of 2 due to spin degeneracy when computing sums over electronic states (i.e. in charge density, occupation matrix, and other quantities). If you take a nonmagnetic
material (e.g. LiCoO2) and model it as a spin-polarized system (nspin=2), the value of U will be the same as when modeling it as nonmagetic (because the magnetization will be zero). So I do not understand why do you have a factor of 2 difference for U in your
simulations.<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
<p><span style="font-size:12.0pt;color:black">Greetings,<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black">Iurii<o:p></o:p></span></p>
<p><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Times",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">--<br>
</span><span style="font-size:12.0pt;font-family:"Cambria",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">Dr. Iurii TIMROV</span><span style="font-size:12.0pt;font-family:"Times",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB"><br>
</span><span style="font-size:12.0pt;font-family:"Cambria",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">Senior Research Scientist</span><span style="font-size:12.0pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">Theory and Simulation of Materials (THEOS)</span><span style="font-size:12.0pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Cambria",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">Swiss Federal Institute of Technology Lausanne (EPFL</span><span style="font-size:12.0pt;font-family:"Cambria",serif;color:gray;mso-ligatures:none;mso-fareast-language:EN-GB">)</span><span style="font-size:12.0pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><a href="http://people.epfl.ch/265334"><span style="font-size:12.0pt;font-family:"Cambria",serif;mso-ligatures:none;mso-fareast-language:EN-GB">http://people.epfl.ch/265334</span></a><span style="font-size:12.0pt;color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><o:p></o:p></span></p>
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<p class="MsoNormal"><b><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">From:</span></b><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"> users <</span><a href="mailto:users-bounces@lists.quantum-espresso.org"><span style="mso-ligatures:none;mso-fareast-language:EN-GB">users-bounces@lists.quantum-espresso.org</span></a><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">>
on behalf of Theo Weinberger <</span><a href="mailto:tiw21@cam.ac.uk"><span style="mso-ligatures:none;mso-fareast-language:EN-GB">tiw21@cam.ac.uk</span></a><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB">><br>
<b>Sent:</b> Tuesday, September 12, 2023 11:21:03 AM<br>
<b>To:</b> </span><a href="mailto:users@lists.quantum-espresso.org"><span style="mso-ligatures:none;mso-fareast-language:EN-GB">users@lists.quantum-espresso.org</span></a><span style="color:black;mso-ligatures:none;mso-fareast-language:EN-GB"><br>
<b>Subject:</b> [QE-users] Spin counting in hp.x with paramagnetic metals</span><span style="mso-ligatures:none;mso-fareast-language:EN-GB">
<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="mso-ligatures:none;mso-fareast-language:EN-GB"> <o:p></o:p></span></p>
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<p class="MsoNormal">Dear Quantum Espresso Users,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I have been using the hp.x code to calculate the Hubbard-U corrections for correlated metallic systems in both their spin-polarised and paramagnetic states.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">In several materials I have noticed that the Hubbard-U value determined for a material in its paramagnetic ground state is approximately twice that compared to when a spin-polarised ground state is assumed (with all other parameters kept
the same).<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I was wondering whether anyone had any insight into how the accounting for spins in occupied Hubbard states works for the hp.x code and whether the paramagnetic implementation of hp.x perhaps counts all spins states twice resulting in this
larger value.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thank you in advance,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Theo Weinberger<o:p></o:p></p>
<p class="MsoNormal">PhD Student<o:p></o:p></p>
<p class="MsoNormal">University of Cambridge<o:p></o:p></p>
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