QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: Manish95 on January 18, 2019, 07:19
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Hi,
I am using QuantumATK 2017.2 version. I am doing band structure calculation for bulk MoS2. I am using ATK-DFT: LCAO, GGA-PBE exchange-correlation, 75 Ha mesh cutoff, 8x8x8 k point, OMX pseudopotential with Medium basis set. But I get band gap 0.89 eV rather than 1.2 eV.
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Could you please explain why you expected 1.2 eV? Is it from a reference where the same computational parameters were used?
Have you converged your calculation with respect to the various computational parameters?
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1.2 eV is the experimental value for bulk MoS2 (Zhiming, MoS2 Materials, Physics and devices). I have converged the calculation.
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0.89 eV is what you would expect for bulk MoS2 if using a LDA or GGA density functional, there are many examples in literature, see e.g. https://file.scirp.org/pdf/Graphene_2014102014384642.pdf
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In addition to the previous post, the band gap is also sensitive to the separation distance, see PHYSICAL REVIEW B 87, 245114 (2013). In the latter, one can also find a comparison of DFT-calculated band gaps to that of GW. The largest gap the authors report with DFT does not exceed 1 eV, see Fig. 4 in the paper.
I also note that stacking of MoS2 monolayers would also affect the band gap value.