[QE-users] Query Regarding optPBE-vdW Functional in QE

[Fabrizio Ferrari Ruffino]

Hello,
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:

input_dft='XC-000i-00​4i-141L-vdw1'

This uses LDA correlation Perdew-Wang + optPBE GGA exchange + vdw1 (M. Dion et al., PRL 92, 246401 (2004))

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.

Hope it helps,

Fabrizio

________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Mitra, Aritra <aritra.mitra at ubc.ca>
Sent: Friday, May 29, 2026 8:57 PM
To: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
Subject: [QE-users] Query Regarding optPBE-vdW Functional in QE

Dear QE Devs/Users,
I am a newbie to QE / DFT simulations in solids.
For my project, I need to implement the optPBE-vdW functional as it agrees well the experimental structures of ice and ionic hydrates.
I noticed that functionals such as optB88-vdW and optB86b-vdW are available through corresponding nametags in funct.f90, but I could not find a similar implementation for optPBE-vdW.
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.
Thank you for your time and assistance.
Best regards,
Aritra

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