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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Dear Xiaohui<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It seems the two DFT+U runs converged to different states for the same atomic configuration, since band gaps and spin densities are quite different. The Hubbard
U term promotes an electron localisation, in your case of the Ti 3d electrons. Different 3d orbital occupation patterns can result in different total energies, especially for large U values. You can check the 3d occupations by activating the &PLUS_U print
section in &FORCE_EVAL/&DFT/&PRINT.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Best regards<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Matthias<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> cp...@googlegroups.com [mailto:cp...@googlegroups.com]
<b>On Behalf Of </b>Xiaohui Yang<br>
<b>Sent:</b> 01 April 2018 14:24<br>
<b>To:</b> cp2k<br>
<b>Subject:</b> [CP2K:10136] DFT+U calculation problems<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">Dear</span><span style="font-size:9.0pt;font-family:".PingFang SC","serif";color:#454545">,</span><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"> all</span><span style="font-size:9.0pt;color:#454545"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">I did some calculations with DFT+U functional recently, they all obtained from the CP2K program. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">At first, I calculated the geometry optimization of the structre, and obtained the total energy directly from the last optimized structure (let's say E1).
Then</span><span style="font-size:9.0pt;font-family:".PingFang SC","serif";color:#454545">,</span><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"> I ran a single point energy calculation with the same optimized structure and
got the total energy E2. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">However, those two total energies (E1 & E2) I collected from the exact same structure have significant difference</span><span style="font-size:9.0pt;font-family:".PingFang SC","serif";color:#454545">,</span><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"> E2-E1
= 1.2 eV. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">When checking their output results</span><span style="font-size:9.0pt;font-family:".PingFang SC","serif";color:#454545">,</span><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">
I find that the total energy difference could be attributed to two parts, DFT+U energy and Core Hamiltonian energy. The input and output files are attached below. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">As far as I know</span><span style="font-size:9.0pt;font-family:".PingFang SC","serif";color:#454545">,</span><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545"> the
total energy calculated from the same settings and structures should be the same. I have no idea about these results. Could you please help me check what is wrong with my calculation? Any comments will be greatly appreciated. </span><span style="font-size:9.0pt;color:#454545"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">Best Regards,</span><span style="font-size:9.0pt;color:#454545"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;font-family:"Helvetica Neue","serif";color:#454545">Xiaohui</span><span style="font-size:9.0pt;color:#454545"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:#454545"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:9.0pt;color:#454545"><o:p> </o:p></span></p>
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