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Hello,</div>
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as far as I can see there is no optPBE among the internal GGA functionals of QE. However, it is available in Libxc. If you want to use it, in combination with vdW, you need to enforce the modified input dft in the QE input file, in &SYSTEM namelist. Here is
an example, where I have put the Libxc exchange 'optPBE' functional in place of the internal 'optB88' GGA exchange one in the 'optB88-vdW' you mentioned:</div>
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input_dft='XC-000i-004i-141L-vdw1'</div>
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This uses LDA correlation Perdew-Wang + optPBE GGA exchange + vdw1 (M. Dion et al., PRL 92, 246401 (2004))</div>
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I am not sure this is exactly what you want, though. More detailed instructions on how to set Libxc functionals in QE are available in the QE user guide (section 'Libxc library') in the Doc folder (user_guide.tex) in the main QE folder. Of course you need a
QE executable compiled with Libxc library (linking instructions are also present in the user guide) in order to use them.</div>
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Hope it helps,</div>
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Fabrizio</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 Mitra, Aritra <aritra.mitra@ubc.ca><br>
<b>Sent:</b> Friday, May 29, 2026 8:57 PM<br>
<b>To:</b> users@lists.quantum-espresso.org <users@lists.quantum-espresso.org><br>
<b>Subject:</b> [QE-users] Query Regarding optPBE-vdW Functional in QE</font>
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Dear QE Devs/Users,</div>
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I am a newbie to QE / DFT simulations in solids.</div>
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<span style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif">For my project, I need to implement the
<code>optPBE-vdW </code></span><span style="font-family:"Aptos","Aptos_EmbeddedFont","Aptos_MSFontService","Calibri","Helvetica",sans-serif"><code style="font-family:"Aptos","Aptos_EmbeddedFont","Aptos_MSFontService","Calibri","Helvetica",sans-serif">functional
as it agrees well the experimental structures of ice and ionic hydrates</code></span><span style="font-family:Aptos,"Aptos_EmbeddedFont","Aptos_MSFontService",Calibri,Helvetica,sans-serif"><code>.</code></span></div>
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I noticed that functionals such as <code>optB88-vdW</code> and <code>optB86b-vdW</code> are available through corresponding nametags in
<code>funct.f90</code>, but I could not find a similar implementation for <code>optPBE-vdW</code>.</div>
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Since optPBE-vdW uses a specific PBE/RPBE exchange mixing (~94.5:5.5) with modified (\mu) and (\kappa) parameters for the GGA enhancement factor, I wanted to ask whether optPBE-vdW is already available in QE under another identifier, or if there is a recommended
way to implement it within Quantum ESPRESSO.</div>
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Thank you for your time and assistance.</div>
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Best regards,<br>
Aritra</div>
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