[QE-users] The difference between DFT-D and DFT-D2 in QE package

[Johannes Meusburger - STFC UKRI]

Hi Mohammad,

Yes you are right  'grimme-d2', 'Grimme-D2', 'DFT-D', 'dft-d' all mean the same thing in Quantum ESPRESSO and refer to the D2 dispersion-correction by Grimme (2006; https://doi.org/10.1002/jcc.20495), which computes a on-the-top two-body dispersion energy. As far as I know, the original DFT - D (or to be more precise DFT - D1) method (Grimme, 2004  https://doi.org/10.1002/jcc.20078) was limited in its application to a small number of elements, and is not used anymore in modern DFT codes (as a user I know it  for Quantum ESPRESSO and CASTEP). Therefore, if authors refer to DFT + D they often mean the DFT + D2 method but please check in the references of the papers you mentioned (i.e., Grimme 2006 --> DFT + D2; DFT + D --> Grimme 2004).

Regarding your second question: Many so called semiclassical dispersion corrections such as D2, D3, TS and MBD are implemented in Quantum ESPRESSO. An alternative approach are the so called non-local functionals such as vdw-DF1, vdw-DF2 and rVV-10. Grimme 2016 (https://doi.org/10.1021/acs.chemrev.5b00533) has written an excellent review article about all of these approaches. I know that it is often very hard to decide for the 'right' approach, especially since you don't have any experimental data for comparison. There are loads of benchmarking studies on the various dispersion corrections, so I would suggest that you choose a correction method that works well for the type of materials you are studying.

HTH,

Johannes
__________________________________________________________________________

Johannes Meusburger
ISIS Neutron and Muon Source, UK
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of mohammad maymoun <maymoun17755 at gmail.com>
Sent: Saturday, February 19, 2022 9:42 AM
To: users at lists.quantum-espresso.org <users at lists.quantum-espresso.org>
Subject: [QE-users] The difference between DFT-D and DFT-D2 in QE package

I am working on decorating 2D materials (carbon based) with halogen atoms. I have readed several papers on decorating 2D materials which include van der Waals correction, some of these papers used DFT-D and others used DFT-D2. But when I looked into the QE package I found that 'grimme-d2', 'Grimme-D2', 'DFT-D', 'dft-d' means the same thing.
I am wondering if this is correct or there is  a misunderstanding of mine.
Please correct me if I am wrong.
I also have another question: there are several  van der Waals corrections available in the QE package including semi empirical and functional. In the absence of experimental data it is difficult to select the compatible van der Waals correction for our material. Because these methods give different formation energy, cell parameters, band gap,.....
could you please give me advice in this regard.

--
Best regards,

Mohammad Maymoun
******************************
PhD Student
Laboratoire des sciences des Matériaux, des Milieux et de la Modélisation (LS3M)
Faculté Polydisciplinaire de Khouribga
Université Sultan Moulay Slimane
Béni Mellal , Maroc


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