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NEGF.tran.Kgrid
Date: 2017/04/26 15:05
Name: mmhs

Dear all

I use openmx to calculate I-V characteristic of 2D nanosheet but i don not know how to choose a correct value for this parameter "NEGF.tran.Kgrid". Can anyone guide me to find a reliable value for this parameter?

When i performed the calculation
the current was (3.559753e-18 ampere) for "NEGF.tran.Kgrid 1 1" ,
and the current was (9.128436e-12 ampere) for "NEGF.tran.Kgrid 15 1".

Thanks in advance
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Re: NEGF.tran.Kgrid ( No.1 )
Date: 2017/04/26 19:05
Name: Artem Pulkin

"Can anyone guide me to find a reliable value for this parameter?"

Larger = better.
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Re: NEGF.tran.Kgrid ( No.2 )
Date: 2017/04/26 23:29
Name: mmhs

Dear Artem Pulkin

But what is the optimum choice for this parameter in 2D nanosheet?
for example "NEGF.tran.Kgrid 30 1" is enough or too large?

Thanks for your reply
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Re: NEGF.tran.Kgrid ( No.3 )
Date: 2017/04/26 23:52
Name: T. Ozaki

Hi,

If your unit cell is narrow along the directions (b- and c-axes) perpendicular
to the transport direction (a-axis) and the bands along those directions are
dispersive, you need to take enough k-points to discretize the Brillouin zone.
Of course a proper choice depends on systems under study, and thereby systematic
benchmark calculations are required to see how quantities you want to calculate
converges as a function of the k-points.

Regards,

TO
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Re: NEGF.tran.Kgrid ( No.4 )
Date: 2017/04/27 20:29
Name: Artem Pulkin

"But what is the optimum choice for this parameter in 2D nanosheet?"

I typically put 400 k-points for publication-quality figures. Sometimes, however, I am interested in high symmetry points only and 3 k-points per unit cell may be enough for me. As prof. Ozaki mentioned, you should adjust every parameter to your particular model and needs. I suggest to start with 20 k-points and double this value until you reach convergence in your I-V curve.
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Re: NEGF.tran.Kgrid ( No.5 )
Date: 2017/04/28 02:37
Name: mmhs

Thanks for your help
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