Does the Grimme D3 correction improve band gaps of vdW heterostructures?

2024-07-02T10:56:21Z

I am doing band structure calculations of 2 by 2 by 1 MoS2/MoSe2 van der Waals heterostructure in Quantum Espresso. I have noticed that adding Grimme DFT-D3 correction to PBE functional has very negligible effect on the obtained band gap from PBE functional alone.

It is an established fact that van der Waals interactions are significant in such structures. So my question is why band gap is not improved?

Answer by Tristan Maxson for Does the Grimme D3 correction improve band gaps of vdW heterostructures?

2024-07-02T17:32:27Z

This is an easy question to probe. Any changes to the total energy, forces, and stress in the post-SCF stage will not change the band gap. Because the D3 correction amounts to such a correction, it does not have a direct influence on the band gap; in fact, you can determine the D3 correction without even running a DFT calculation.

The influence will come in by the change in geometry. If you compress or decompress the structure, do you see changes in band gap? If so, the stress contribution from D3 may play a role in the band gap of your material. Similarly, D3 may change the stable positions of less rigid parts of a crystal structure which will also affect band gap.

I should also stress this will happen when using D2, D3, D4 or any other vdW approach which is simply an emperical energy, force, stress correction ontop of a DFT calculation.

Does the Grimme D3 correction improve band gaps of vdW heterostructures? - Matter Modeling Stack Exchange

Does the Grimme D3 correction improve band gaps of vdW heterostructures?

Answer by Tristan Maxson for Does the Grimme D3 correction improve band gaps of vdW heterostructures?