Messages

1

General Questions and Answers / Re: Calculation of doping concentration

« on: September 1, 2020, 20:21 »

Thanks sir
 This is very helpful for me

2

General Questions and Answers / Re: Regarding bandstructure difference between unit cell and repeated cell

« on: September 1, 2020, 14:02 »

Yes sir, Dos is same but the bandstructure is not matching. I have communicated a manuscript with this bandstructure and they are asking about the bandstructure matching. Can you please suggest the high symmetry brilliouin zone point for the bandstructure calculation. How can I defend this problem.

3

General Questions and Answers / Regarding bandstructure difference between unit cell and repeated cell

« on: September 1, 2020, 11:11 »

Dear sir, I have calculated the bandstructure of unit cell and its repeated cell the bandstructure of both the system are different. I have calculated the bandstructure of unit cell for brillioun zone point X, Z T, Y, G which is in well agreement with reference literature 10.1016/j.physb.2018.02.015. but when I have repeated the cell than the bandstructure is not sane as unit cell. I have tried all possible brillioun zone point. But the bandstructure is not matched. Please help me out
Related Log files and py files are attached
Thanks in advance
Sonal

4

General Questions and Answers / Basis set superposition error correction

« on: August 31, 2020, 14:36 »

Dear sir,
Is basis set superposition error correction i.e. counterpoise correction is necessary in sensing of molecules on a sheet. is this error cause large variation from the experimental results as given in the manual of counterpoise correction or we may consider only vanderwall interaction and ignore counterpoise correction.

5

General Questions and Answers / Re: Calculation of doping concentration

« on: August 16, 2020, 11:07 »

Thanks for your reply

Sir, I have not doped the hydrogen atom. I have introduced doping in the middle of  the nanoribbon by replacing carbon atoms. Then I am calculating  doping concentration of dopant atoms. In this case, we should take hydrogen concentration into account or not?



Thanks in advance
sonal

6

General Questions and Answers / Calculation of doping concentration

« on: August 9, 2020, 10:17 »

Dear sir,
When we doped the nanoribbons then in the calculation of doping concentration we should take hydrogen atom into account or not?? Is the hydrogen atoms are only for avoiding the dangling bond or we should considered the concentration of hydrogen atoms while calculating the concentration.

7

General Questions and Answers / Re: error in IdVg Calculation

« on: June 13, 2020, 14:27 »

I am also facing same problem

8

General Questions and Answers / Re: Calculate fermi velocity

« on: June 12, 2020, 19:44 »

It's easy

K = (1/3,1/3,0) in units of the inverse lattice vectors GA=2pi/a*(1,1/sqrt(3),0) and GB=2pi/a*(1,-1/sqrt(3),0). Hence, K=4pi/3a*(1,1,0) in reciprocal Cartesian.
(We had LaTeX support on the Forum before, I lost it in an update... should bring it back.)

So, K-eps*(1,1,0)=(4pi/3a)*eps*(-1,0,0) and hence dK = 4pi/3a*eps.

Dear sir,
The method given in the above-quoted post  Is the same method i.e. used in the calculate velocity function given in the tutorials of calculation of Fermi velocity in ATK-VNL.
From the tutorial, I am getting the Fermi velocity of silicene and graphene in the 10^5 and 10^6 which is in good agreement in literature but in case of germanene, I am getting only 10^2 m/s. 
Thanks in advance

9

General Questions and Answers / Re: Fermi velocity in zigzag graphene nanoribbon

« on: May 22, 2020, 12:25 »

Dear sir,

 As given in the manual of calculate velocity function fermi velocity of graphene is calculated at the valance band maximum band (In the case of graphene band indices 3). In my case as I said multiple bands are crossing the Fermi level than I should calculate the velocity only those valance bands which crosses the fermi level or both conduction and valance band crossing the Fermi level.

2. If bandgap is present in the system in that case which bands should be considered for calculating velocity.


Thanks in advance
sonal

10

General Questions and Answers / Re: Differene between zero bias conductance in bulk mode and device mode

« on: May 19, 2020, 19:42 »

Thanks for clarifying this

I have one more question.
Can we connect the electrode in a hexagonal sheet of graphene in ATK-VNL?

11

General Questions and Answers / Re: Brillouin zone in bandstructure of graphene nanosheet

« on: May 18, 2020, 19:44 »

Thanks for your help
This is really helpful for me

12

General Questions and Answers / Re: Differene between zero bias conductance in bulk mode and device mode

« on: May 18, 2020, 19:39 »

Thanks for your response

Yes, you are right I can not compare DFT and extended huckle results.
But I ask this question because I have calculated the transmission spectrum for pristine graphene using extended huckle and DFT calculator and I am getting the same conductance using both but in case of doped graphene, I am getting different results.

Thanks & Regards
sonal

13

General Questions and Answers / Re: Fermi velocity in zigzag graphene nanoribbon

« on: May 18, 2020, 19:23 »

Thanks for the help.


Is the value of Nch depends on the band crossing the Fermi level, I have calculated this by calculating the no. of transmission modes.
As you told I have to calculate this for each band that crossing the Fermi level. But in my case, this is the same for all the bands.
Is am I doing something wrong?
please clarify this.
 

14

General Questions and Answers / Re: Brillouin zone in bandstructure of graphene nanosheet

« on: May 15, 2020, 11:23 »

Thanks for suggestion.
 
Iincreasing k point sampling improves the bandstructure but not exactly zero.
 I m getting bandgap of 0.07  in the G, Z direction, which is approximately zero, when I am selecting Full Brillouin zone points  G, Z, G, Y, Z than I am getting the same bandgap as G, Z however if I am selecting only G, Y then I m getting bandgap of 2.023eV, Which means it totally depends on the selection of Brillouin zone points.
1.  How can we identify which Brillouin Zone point should be select in the bandstructure?

 2. Nanosheet is periodic in both directions than why we are taking more K points in one direction than others.
 please clear my doubts.

Thanks & Regards
sonal

15

General Questions and Answers / Re: Differene between zero bias conductance in bulk mode and device mode

« on: May 15, 2020, 10:34 »

Dear sir,
Thanks for your response
 I am using quantum ATK-2019.03
Related log files and python files are attached herewith.
Sir, I have two more question
1. If we analyzed the electronic properties using DFT LCAO calculator, phonon properties using Forcefield and transport properties using extended huckle than the results will be valid or not.
2. Is the electrode size affect the I-V characteristics if the structure is perfect, I mean there is no defects and doping in the structure and if defects and doping are present.

Thanks & Regards
sonal