| Re: Band gap and DFT-D3 ( No.1 )|
- Date: 2022/12/07 11:58
- Name: T. Ozaki
I think that the band gap of 0.65 eV for the WS2/GaS double layer is a proper result within GGA-PBE.
The gap of the double layer is mainly contributed by the WS2 layer rather than GaS, and
the small band gap is due to the in-plane lattice constant in the double layer.
From Materials Project, the in-plane lattice constants optimized by the GGA-PBE are found to be
3.191 Ang. for WS2 bulk
3.627 Ang. for GaS bulk
So, the average lattice contant is (3.191+3.627)/2 = 3.409 Ang. consistent with yours.
Then, each monolayer exhibits the following band gaps:
WS2 1.78 eV at 3.191 Ang.
WS2 0.82 eV at 3.409 Ang.
GaS 2.65 eV at 3.409 Ang.
Thus, it turns out that the expansion of the in-plain lattice constant for WS2 layer largely reduces the gap,
while the GaS still keeps the large gap.
The similar behavior has been reported at https://doi.org/10.1039/C4RA06378C
By considering a fact that the interaction between the WS2 and GaS layers in the double layer makes the band width wider,
the gap (0.82 eV) of the WS2 molayer must become smaller in the double layer, resulting in the gap of 0.65 eV
in the double layer.
| Re: Band gap and DFT-D3 ( No.2 )|
- Date: 2022/12/07 10:49
- Name: Vicky
- Dear Professor Ozaki,
Thank you very much for your prompt reply. I understand now the reason behind the reduced band gap.