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QuantumATK => General Questions and Answers => Topic started by: paramjot on March 19, 2020, 20:49

Title: Band Structure and Density of States
Post by: paramjot on March 19, 2020, 20:49

I made a structure of doped graphene and obtained its bandstructure and DOS. bandstructure is showing a bandgap of 0.45eV whereas at the same energy level the DOS chart showing some states instead of being value zero. I have all attached all the pictures. Can anybody tell me the reason?

Title: Re: Band Structure and Density of States
Post by: NW on March 20, 2020, 16:31

Hi,

It is better to obtain the band structure in other routes of Brillouin zone.

Title: Re: Band Structure and Density of States
Post by: Petr Khomyakov on March 23, 2020, 01:55

Quote from: paramjot on March 19, 2020, 20:49

I made a structure of doped graphene and obtained its bandstructure and DOS. bandstructure is showing a bandgap of 0.45eV whereas at the same energy level the DOS chart showing some states instead of being value zero. I have all attached all the pictures. Can anybody tell me the reason?

Please post your python scripts and related log files for these calculations.

Title: Re: Band Structure and Density of States
Post by: paramjot on March 23, 2020, 23:16

all relevant files are attached

Title: Re: Band Structure and Density of States
Post by: Nayab Shiraz on March 23, 2020, 23:20

Hi
I am having a similar issue when I try to plot DOS for carbon nanotube (10,0) which is definitely semiconducting and has a bandgap. Bandstructure shows the bandgap but DOS shows a small value at fermi level. However when I plotted the same DOS in older version 13.8.1 this issue was not there. Now I have 2019 version and it gives this issue.

Title: Re: Band Structure and Density of States
Post by: paramjot on March 24, 2020, 20:31

Mr Petr can you please where I made a mistake?

Title: Re: Band Structure and Density of States
Post by: Petr Khomyakov on March 25, 2020, 16:39

You should try increasing k-point sampling for DOS calculation. I have attached a modified script that does that and also it includes 2 methods to compute DOS; for your system, you should decrease the Gaussian broadening such that the spectrum is not too broadened to close the gap.

I would also advise to use a more general analysis object (also available through GUI), https://docs.quantumatk.com/manual/Types/LocalDensityOfStates/LocalDensityOfStates.html, where you may change this broadening parameter and even set DOS method to tetrahedron method that does not require broadening parameter, but it requires a number of k-points, as used in the script enclosed.

Title: Re: Band Structure and Density of States
Post by: paramjot on March 25, 2020, 22:33

Thanks Sir! got positive result