About alignment of 2D monolayer band structures

[alok_shukla1]

Dear Experts and All,
I need to do the alignment of band structures of one 2D monolayer. I have created some vacancies in the 2D monolayer and calculated the band gap values (GGA) corresponding to different considered vacancies along with the pure monolayer. I understood that for alignment, I need to identify a common reference potential, such as the vacuum level, that could serve this purpose. An alignment to the vacuum level is equivalent to an alignment to the average electrostatic potential (Phys. Rev. B 84, 125206 (2011). I have calculated the average electrostatic potential for pristine monolayer and for defective cases. Now, I am not getting how to select the reference point or how to align the valence band and conduction band corresponding to that reference point. Also, please suggest me if there is anything else (some other calculations) I need to do.

[fabien_tran1]

Hi,

It is not completely clear which final quantity/property you would like to obtain. So, please try to explain more clearly what is your goal. Besides, how did you calculate the average electrostatic potential? As the average in the whole unit cell including the vacuum?

[alok_shukla1]

I am interested in band edge alignment (valence band and conduction band edges). For the average electrostatic potential calculation, in my monolayer, in which the vacuum is around 21 Angstrom, I kept the same POSCAR and added LVTOT = .TRUE. in the INCAR, and took the average of LOCPOT generated data. Yes, the average is in the whole unit cell, including the vacuum. Please correct me if my understanding is incorrect.

[fabien_tran1]

I am not a specialist of this topic, but I would say that a possible choice for the common reference potential could be the electrostatic potential in the middle of the vacuum. Taking the average in the whole unit cell does not really seem meaningful, since the value will depend on the size of the vacuum.

[alok_shukla1]

I understood that it is a vacuum-dependent thing. I'll try to explore this topic more by reading other literature. Thank you so much for your response.