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QuantumATK => General Questions and Answers => Topic started by: Monika srivastava on May 21, 2020, 16:42

Title: Mismatch of bandstructure and density of states
Post by: Monika srivastava on May 21, 2020, 16:42

Dear Sir
I have computed the band structure and dos for gas adsorbed cu ion  decorated n doped graphene but it does not matches although i have varied my k points (increased) but it did not matches the band gap obtained in dos is smaller then the band gap obtained from band structure.

Thank you in advance

Title: Re: Mismatch of bandstructure and density of states
Post by: Tue Gunst on May 22, 2020, 09:01

Hi, If you increase the k-point sampling (in the 2D periodic directions) they will correspond to each other.
You can try to compare the DOS spectra obtained with either gaussians or the tetrahedron methods as described in the example in the reference manual:
https://docs.quantumatk.com/manual/Types/DensityOfStates/DensityOfStates.html

Alternatively it could be that your k-point route used in the bandstructure does not contain the point where the minimal gap is located. The DOS integrate over all k-points in the Brillouin zone.

Title: Re: Mismatch of bandstructure and density of states
Post by: Monika srivastava on May 22, 2020, 15:12

Thank you sir for your valuable reply but,

I have tried guassian but still it is mismatched.

so "Alternatively it could be that your k-point route used in the bandstructure does not contain the point where the minimal gap is located" for this what should i do. 

Title: Re: Mismatch of bandstructure and density of states
Post by: Petr Khomyakov on May 25, 2020, 14:26

Regarding computing DOS for graphene see Appendix in Phys. Rev. B 87, 075414 – Published 7 February 2013. As Tue suggested also try increasing the number of k-points significantly. Did you also use tetrahedron method with significantly increased k-point density? It would also be helpful to see your script.

Title: Re: Mismatch of bandstructure and density of states
Post by: Monika srivastava on May 20, 2025, 13:57

Could you please have a look with script I tried different smearing different k points different functional but band gap through band structure  and band gap through dos is not matching

Title: Re: Mismatch of bandstructure and density of states
Post by: Anders Blom on May 23, 2025, 21:38

When we say increase k-point signficantly, we mean 200x200 or 300x300 points.

Title: Re: Mismatch of bandstructure and density of states
Post by: Monika srivastava on May 26, 2025, 15:26

this is two large i am not able to go such large k points in our system. is there any way.

Title: Re: Mismatch of bandstructure and density of states
Post by: Anders Blom on May 27, 2025, 20:49

You do not need this number of k-points in the main calculation, only for the DOS.