Topics

1

General Questions and Answers / how to set the dopants

« on: May 24, 2012, 13:50 »

hi, every body,

I want to calculate the doped semiconductor. As we know, the donor or acceptor impurities are charged, such as the P atom is positive ion after substituting the Si atom. So, How can I set up the simulation model in which the impurity atom replace the host atom ? I used the P or B atom simply replace the Si atom, and got the band structure which indicates the doped Si bulk acts as N or P type semiconductor. But, the Mulliken popular of the P atom show that the p atom is negtive ion. How to undertand this issue ? Should I make the doped P atom positive during the calculation ?

Any suggestion is great appreciated !

 

2

General Questions and Answers / how to analysis the band structure of B-doped armchair graphene ribbons

« on: March 1, 2011, 06:24 »

hi，
I recently calculated the energy band structure of B-doped armchair graphene ribbons, but I did not know how to analysis it. I have enclosed the figure of energy band structure of intrinsic and B-doped armchair graphene ribbons. In that figure, the left figure is for intrinsic armchair graphene ribbons and the right figure is B-doped armchair graphene ribbons. obviously  intrinsic armchair graphene ribbons is a semiconductor, but  is it B-doped armchair graphene ribbons semiconductor ? Is that can be deduced from the energy figure ? B-doped armchair graphene ribbons seems a metal, am I right ?

can any one help me to analysis it ? any suggestion is appreciated ! thank you !

3

General Questions and Answers / why the fermi energ level locates blow the valence band ?

« on: December 12, 2010, 10:05 »

Hello, every body,

I calculated the band structure of doped graphene ribbon recently, but the figure I obtained confuses me. the fermi energy locats below the valence band when it is doped. the fermi energy is -4.37 eV for intrinsic GNRs but -5.07 eV for doped GNRs. can anyone help me to explain the phenomenon? any suggestion is appreciated. thank you !
the figure have been attached.

4

General Questions and Answers / how to build the graphene nanoribbons?

« on: June 23, 2010, 04:35 »

Hi,
I want to build the graphene nanoribbons. So I download the graphene_ribbon.py file from the http://quantumwise.com. However, when I drug it into the VNL, It does not work. can anyone details the method of building the graphene nanoribbons? Thank you !

5

General Questions and Answers / how to build the silicon nano-wire?

« on: June 8, 2010, 09:47 »

hello,
I want to calculate the energy band of silicon nano-wire, but I don't know how to build it with VNL. Can any one show me the details? thank you!

6

General Questions and Answers / How to set to make the iSCF converge?

« on: May 30, 2010, 14:43 »

hello, everyone
The set I made for scf calculation are listed as follow:
the energyshift 50 meV, ElectronicTemperature 300 K, DM.MixingWeight 0.25, DM.NumberPulay 6, mesh Cutoff 240 Ry,MaxSCFIterations 500
but,  it can not converge for scf calculation.

Are there any other parameters to be set for convergence of DM scf calculation? please help me ! thank you ! the elements used in that calculation are C, B, P.

7

General Questions and Answers / can ATK calculate the optical characteristic?

« on: May 5, 2010, 06:39 »

Hello, every body!

I want to use the VNL to calculate the optical characteristic, but I don't know how use it! Does anybody show me the details?

8

General Questions and Answers / how to build the doped single wall carbon nanotubes?

« on: April 28, 2010, 08:22 »

Hi, everbody,
 I want to build doped single wall carbon nanotubes using the VNL, but I don't know how to build it. anyone can show me the details? please help me! thank you!

9

General Questions and Answers / how can I get the results from the .nc file?

« on: July 27, 2009, 04:31 »

Hi,
I have calculated my job which calculated the I-V curve by making a loop, but I closed the .log file. Now, I want to see the results again, but when I put the .vnl file into the results browser, I cant no t see the all the results any more, it just show the last  value of the current. How can I get all the values of the current under different bias?

10

General Questions and Answers / is the reults of current correct?

« on: May 11, 2009, 11:35 »

hi, everybody.
I calculate the I-V characteristic using the method as follow:
1.  calculate the current under zero bias and get the zerobias.nc
2. calculate the current under a high bias such as 4 Voltage and get the 4voltage.nc using the date of zerobias.nc.
3. then the bias descrease in the step of 0.5 Voltage. serials valence of current under different bias can be got using the date of 4voltage.nc as the initial data. I find that the convergence can be quickly attained.

so, I don't sure the results of current is precise? can anybody give a some suggestion?

11

General Questions and Answers / How can I rerun the job?

« on: May 9, 2009, 06:52 »

hello, verybody.
I want to ask that when the running job is broken, I want to continue this job after its break. How can I retart the job?

12

General Questions and Answers / Re: can VNL calculate the variation of the current as a function of voltage?

« on: April 27, 2009, 09:53 »

dear
 I have edited the script followed what you describe ,but when the job run, SyntaxError: invalid syntax (c:/users/617/appdata/local/temp/tmpwdhrmo.nl, line 419) comes out.
my script is edited as follows:


from ATK.TwoProbe import *
from ATK.MPI import processIsMaster
import numpy%