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<p>Dear Jacob,</p>
<p><br>
</p>
<p><span style="font-size: 11pt; font-family: "CMU Bright Roman", serif, "EmojiFont";">> d^2E_xc / drho(r) drho(r’)</span><br>
</p>
<p><br>
</p>
<p>This is dV_xc/drho which is the second term in Eq. 13 in PRB 88, 064301 (2013). Equations 12 and 13 of this reference are implemented in the routine
<span>LR_Modules</span>/<span>dv_of_drho.f90</span><br>
</p>
<p><br>
</p>
<p><span style="font-size: 11pt; font-family: "CMU Bright Roman", serif, "EmojiFont";">> chi(r,r’, omega=0) = drho(r)/dv(r’)</span><br>
</p>
<p><br>
</p>
<p>The response charge density drho is computed in the routine <span>LR_Modules</span>/<span>incdrhoscf.f90</span></p>
<p><br>
</p>
<p>In the TDDFPT codes in QE the density-density response is computed using the Lanczos or Davidson algorithm, see e.g. Eq. 17 in the aforementioned paper. See also Eq. 3 in PRB 102, 035156 (2020).</p>
<p><br>
</p>
<p>HTH</p>
<p><br>
</p>
<p>Greetings,</p>
<p>Iurii<br>
</p>
<p><br>
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<font size="3" face="'Times New Roman', Times, serif" color="808080">--<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> developers <developers-bounces@lists.quantum-espresso.org> on behalf of Jacob Williams <jacob.z.williams@duke.edu><br>
<b>Sent:</b> Monday, May 9, 2022 7:48:00 PM<br>
<b>To:</b> developers@lists.quantum-espresso.org<br>
<b>Subject:</b> [QE-developers] Static density response and xc kernels</font>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman"">Dear all,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman"">I am working on implementing the LOSC correction for DFT (see, e.g., arXiv:2202.01870) in QE 7.0, and am in need of calculating the zero-frequency density-density response [chi(r,r’,
omega=0) = drho(r)/dv(r’)] (or its plane-wave representation), as well as the exchange-correlation kernel [d^2E_xc / drho(r) drho(r’)]. Note that I’ve suppressed spin indices.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman"">Is this possible to do with existing routines? I know the capability must exist, because more powerful versions (the full frequency-dependent response) are used by TurboEELS
and co, but I haven’t been successful in finding how to compute the static quantities in the code. I thought the response function might be obtainable from the Kohn-Sham responses dpsi obtained from LR_Modules/response_kernels.f90, but I’m not sure how to
connect that to the full response function.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman"">Thank you in advance for your time and your help!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman""><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman";color:black">Sincerely yours,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman";color:black"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman";color:black">Jacob Williams<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman";color:black">PhD candidate, Weitao Yang group<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"CMU Bright Roman";color:black">Duke University Department of Chemistry
</span><o:p></o:p></p>
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