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General Questions and Answers / Re: Current segregation and whether higher T(E) guarantee higher current?
« on: May 17, 2016, 20:42 »
Could any one please answer?
Thanks!
Thanks!
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General Questions and Answers / Current segregation and whether higher T(E) guarantee higher current?
« on: May 14, 2016, 15:13 »
Would anyone kindly tell me how I can calculate or segregate the currents due to different the different charge carriers of different spins? (eg. how much is the current due to the up spin holes alone?) I have only the transmission spectra, and DOS of the spin polarized device.
Another question is that, as per the simulation results I see that higher T(E) is not guaranteeing higher current (eg. I increased the bias, and current increased with as the bias increased but the summation of T(E) over the entire range of energy (in which the calculation was made) or even near the fermi energy is decreasing with increment in bias).
So, if higher T(E) does not guarantee higher current then what can we comment about current when the bias is kept same but the summation of T(E) decreases or increases in different Nanoribbons?
Another question is that, as per the simulation results I see that higher T(E) is not guaranteeing higher current (eg. I increased the bias, and current increased with as the bias increased but the summation of T(E) over the entire range of energy (in which the calculation was made) or even near the fermi energy is decreasing with increment in bias).
So, if higher T(E) does not guarantee higher current then what can we comment about current when the bias is kept same but the summation of T(E) decreases or increases in different Nanoribbons?
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General Questions and Answers / Re: No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: January 21, 2016, 05:47 »
Could you please tell me which of the following codes must I use for analysing the transmission spectrum using adaptive grid (in 2015 version)
OR
Code
# -------------------------------------------------------------
# Setup adaptive grid object.
# -------------------------------------------------------------
adaptive_grid = AdaptiveGrid(
kA_range=[-0.5, 0.5],
kB_range=[-0.5, 0.5],
tolerance=1e-2,
error_measure=Absolute,
number_of_initial_levels=4,
maximum_number_of_levels=8)
# -------------------------------------------------------------
# Transmission Spectrum
# -------------------------------------------------------------
transmission_spectrum = TransmissionSpectrum(
configuration=configuration,
energies=numpy.linspace(-5,5,501)*eV,
kpoints=adaptive_grid,
energy_zero_parameter=AverageFermiLevel,
infinitesimal=1e-06*eV,
self_energy_calculator=KrylovSelfEnergy(),
)OR
Code
# -------------------------------------------------------------
# Setup adaptive grid object.
# -------------------------------------------------------------
adaptive_grid = AdaptiveGrid(
kA_range=[-0.5, 0.5],
kB_range=[-0.5, 0.5],
tolerance=1e-2,
error_measure=Absolute,
number_of_initial_levels=4,
maximum_number_of_levels=8)
# -------------------------------------------------------------
# Transmission Spectrum
# -------------------------------------------------------------
transmission_spectrum = TransmissionSpectrum(
configuration=configuration,
kpoints=adaptive_grid,
)4
General Questions and Answers / Re: No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: January 1, 2016, 19:48 »
Wow! That seems interesting.
Could you please provide a tutorial or two on how to incorporate it effectively?
Also, it would be great if you would kindly share some insights on:
i) what would the k range (say from -0.1 to 0.1) actually mean? Does this improve the accuracy?
ii)whether we have to make sure that the range always adds up to 1, if that is the case then how do we decide the value of the floats?
Thank you very much for your reply!
That seems interesting.Could you please provide a tutorial or two on how to incorporate it effectively?
Also, it would be great if you would kindly share some insights on:
i) what would the k range (say from -0.1 to 0.1) actually mean? Does this improve the accuracy?
ii)whether we have to make sure that the range always adds up to 1, if that is the case then how do we decide the value of the floats?
Thank you very much for your reply!
5
General Questions and Answers / Re: No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: December 29, 2015, 16:39 »
Thank you for your reply.
Yes, Recursion takes a lot of computational time that is why I cannot perform the convergence test (for k of TS) for the system while working with Recursion. So, i am searching for a way to perform the convergence test quickly and then use the same no. of k points and do the calculation in Recursion (if possible i.e. if the test stays valid to some extents, irrespective of the self energy calculator). Could you please suggest something for the goal?
Yes, Recursion takes a lot of computational time that is why I cannot perform the convergence test (for k of TS) for the system while working with Recursion. So, i am searching for a way to perform the convergence test quickly and then use the same no. of k points and do the calculation in Recursion (if possible i.e. if the test stays valid to some extents, irrespective of the self energy calculator). Could you please suggest something for the goal?
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General Questions and Answers / Re: Question about calculating Work function of metal
« on: December 29, 2015, 10:43 »
Okay got it! Thank you very much!
7
General Questions and Answers / Re: Question about calculating Work function of metal
« on: December 28, 2015, 20:46 »Draw the plot of the planar average of ElectrostaticDifferencePotential and see whether the curve at the vacuum region is flat or not.
If the vacuum thickness is too thin, the curve at the center of vacuum region may not flat. In this case, you have to increase the vacuum thickness.
I have added vacuum by changing the lattice parameters and then created a device (simply from bulk to device) and then calculated the ElectronDifferencePotential.
I cannot find much difference, i.e. the curve at the centre of the vacuum region seems to be flat in all the three cases (5A, 10A and 20A vacuum on sides of the width of the ribbon as well as above and below the surface of the ribbon)
C direction is the transport direction where the electrodes are located.
B implies the width of the ribbon.
A is direction perpendicular to the surface.
Could you please tell me how much amount of vacuum must be incorporated for further calculations?
Thanks in advance!
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General Questions and Answers / Re: proper basis sets of extended Huckel, for hexagonal BN-C nanoribbons
« on: December 26, 2015, 18:26 »
Then which calculator should one go for such a system?
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General Questions and Answers / Re: No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: December 26, 2015, 18:23 »
Could anyone kindly answer this?
10
General Questions and Answers / Re: Question about calculating Work function of metal
« on: December 25, 2015, 20:41 »
Oh okay! Thank you very much!
Merry Christmas!
Merry Christmas!
11
General Questions and Answers / Re: No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: December 25, 2015, 05:23 »
Here by k-point I mean sampling in the Transmission spectrum analysis (nA)
Please reply
Please reply
12
General Questions and Answers / Convergence test for vacuum thickness
« on: December 25, 2015, 05:20 »
Thank you Umberto and zh.
The subject probably misdirected my question.
I am not trying to find the work function. I am simply unable to decide how much vacuum around the nanoribbon is necessary (specifications mentioned in my previous post). I read here that one must check for convergence of vacuum thickness. I want to know the procedure for checking the convergence.
The subject probably misdirected my question.
I am not trying to find the work function. I am simply unable to decide how much vacuum around the nanoribbon is necessary (specifications mentioned in my previous post). I read here that one must check for convergence of vacuum thickness. I want to know the procedure for checking the convergence.
13
General Questions and Answers / No. of k point for convergence of transmission spectrum (Krylov/Recursion)
« on: December 23, 2015, 06:45 »
In the tutorial http://quantumwise.com/documents/tutorials/latest/ATKTutorialDeviceNew/index.html/chap.zerobias.html#sect1.zerobias.convergence
I saw that one must check the convergence of k points of transmission spectrum.
If I check for the convergence while using Krylov self-energy calculator and get the no. of k points for which the calculation converges and then use the same k for calculating using Recursion, will it be a problem? Or do I have check for convergence separately for Recursion?
I saw that one must check the convergence of k points of transmission spectrum.
If I check for the convergence while using Krylov self-energy calculator and get the no. of k points for which the calculation converges and then use the same k for calculating using Recursion, will it be a problem? Or do I have check for convergence separately for Recursion?
14
General Questions and Answers / Re: Landau-Lifshitz-Gilbert formula for spin transport?
« on: December 22, 2015, 19:20 »
Oh okay! And that is accurate enough? 
15
General Questions and Answers / Re: Question about calculating Work function of metal
« on: December 22, 2015, 19:02 »
How does one perform a convergence test for vacuum thickness for vacuum on the sides (along the width) of a nanoribbon? Does the procedure vary with calculator or material? I plan to use DFT GGA.RPBE calculator for Silicene. How must I check for the best vacuum for the sheet 10 atoms wide, 10 atoms long sheet?