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Messages - Anirban Basak

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1
Installation and License Questions / Re: Pause/Restore simulation after network failure (in Parallel)
« on: May 5, 2012, 11:16 »
Hmm. Can we not increase the license time-out to say 1 hr, so that the simulation waits for sufficiently long time before it stops?

2
Installation and License Questions / Re: Assymetrical core distribution (in Parallel)
« on: May 5, 2012, 10:28 »
Thank you !!! This works very fine  :D

3
Installation and License Questions / Assymetrical core distribution (in Parallel)
« on: May 4, 2012, 14:53 »
Hi,

           If I have two 12 core machine and one 80 core SUN machine, can I some how define which node has how many cores and make the program run such that each 12+12+80 cores are utilized? I tried to simply include the ip of SUN machine and increase the number to 12+12+80, and mpich2 just roughly divided it by 3 and allocated it symmetrically.

Thanks

4
Installation and License Questions / Pause/Restore simulation after network failure (in Parallel)
« on: May 4, 2012, 14:48 »
Hi,

           I have two 12 core machine in our lab and a 80 core SUN server in other lab. The license server is one of the two machine in our lab. I am trying to run a simulation over the SUN machine. But we have some power failures and the simulation gets killed without the license. Is there any way to pause the simulation automatically (when network fails/no license) and resume it again automatically (when power comes back)? The simulation will be waiting for the license to become available again and not get killed (like Synopsys TCAD Sentaurus).

Thanks

5
General Questions and Answers / Re: Obtaining Energy band diagram
« on: April 3, 2012, 19:28 »
Yay.  ;D

Well, how do I get this potential profile for Device Calculated by Huckel ?

6
General Questions and Answers / Obtaining Energy band diagram
« on: April 3, 2012, 12:31 »
Hello,

        How to obtain Energy band diagram (E vs. x) to visualize band bending of conduction and valence band?
        I have a guess that I have to find an effective potential profile w.r.t. fermi energy and adjust the band minima w.r.t that value.
        Am I right?

Thanks

7
Scripts, Tutorials and Applications / Re: Negative Current obtained from positive bias Voltage
« on: March 10, 2012, 12:24 »
Thank you very much for the enlightment on the number of k-points.

I'd like to state a trend I've seen in bias point calculation. A system which is difficult to converge, converges easily if the mesh cutoff is increased without changing k-points. However this thing does not scale linearly with bias points. Sometimes a high bias point may be easier to converge than low bias point.

I also have a question. Say I've converged upto some bias points with 50 Hartree cutoff. Now I face difficulty in convergence and try to increase the cutoff to 100 or such Hartree for further bias points. Does the wavefunction data that gets saved becomes bulky onwards (like it is saved for more closely spaced real axis points)? Any problem if I do this?

Another thing is that I had inspected Pt and ZZ CNT contacts and it converged for all biases (in one step! even when bias is changed) where the mesh cutoff was 10 Hartree. After calculating current I got them around 1E-20 A. I think it is non-physical. Should I increase the mesh-points and redo my calculation?

8
Scripts, Tutorials and Applications / Re: Negative Current obtained from positive bias Voltage
« on: February 20, 2012, 11:11 »
Thank you Anders. You are amazing.  :)

BTW, say I have converged my calculation with 3x3x100 k-pts. While I calculate transmission spectra should I reduce them to 1x1x100 or 3x3x10 or keep 3x3x100 ? (the goal is again to speed up  ;) without loosing much accuracy of course)

9
Scripts, Tutorials and Applications / Re: Negative Current obtained from positive bias Voltage
« on: February 15, 2012, 07:18 »
Thank you Anders. I wrongly assumed for SE all basis has same cut-off. So I did not use to attach calculator while checking.

I see both Hoffman and Cedra DOS for Pt shows generally metallic characteristics. So I think I'd go for the faster one (Hoffman). BTW, what is Muller basis good for?

Also how lagre can I keep the convergence tolerance for a (well if not reasonably good) moderate accuracy in I-V analysis ? (It would be good if I can limit number of iteration for each bias around 10)
I used Hoffman and after around 10 iterations dH = 4 Hartree. The rate of dH decrement was also 1 Hartree/iteration. However, dE was comparatively lower like around 1e-2.

10
General Questions and Answers / Re: My First TFET
« on: February 15, 2012, 06:56 »
Hi esp, i think i will try to answer some of your questions.

1) In this case you have to consider the fringing fields from your gate. If you use high-k dielectric i guess the electric field will not fringe too much and you can use smaller gate.

2) You should remember that the voltage drop you apply actually appears across the scatterer (i.e. the left source, the channel and the right drain region) all encapsulated in the middle box as a single structure. The electrode you use in ATK does not get voltage drop and is only there to provide self-energy for the left side of source and the right side of drain. In simple word if in your device structure if you ignore the left and right electrode box and consider the remaining structure, that is where the voltage drops.  ;)

for 3 I dont have much ideas to tell hehe  ;D

11
Scripts, Tutorials and Applications / Re: Negative Current obtained from positive bias Voltage
« on: February 14, 2012, 05:18 »
But Anders, Huckel requiring more basis set length goes against the electrode length checker script. Thus I'm puzzled.  ???

The DFT is proving to be way too much time consuming and a resource hog in my system. It fills up all my RAM and swap space and asks for more  :o

Also does nonSCF Huckel tries to converge at best possible state in one step while SCF Huckel just tries to match the tolerance in a number of steps?

EDIT: I mean are the nonSCF calculation and the first iteration of SCF calculation exactly same?

12
Scripts, Tutorials and Applications / Re: Negative Current obtained from positive bias Voltage
« on: February 13, 2012, 07:14 »
Is there ANY way to get rid of negative transmission spectra in Huckel calculation? I did as suggested in above but did not work.

13
Scripts, Tutorials and Applications / Re: 1d DOS script port
« on: January 16, 2012, 13:37 »
Thank you. Anders. I can do it now.   :)

14
Scripts, Tutorials and Applications / Re: 1d DOS script port
« on: January 16, 2012, 12:56 »
Yeah. But that gives me DOS curves which does not look like what should be for 1D systems. It seems there is no way to configure the DOS calculation to be done in 1D. I'm talking about something you did here - http://quantumwise.com/forum/index.php?topic=261.msg1512#msg1512. The CNT DOS here really looks like for 1D system (without broadening).

15
Scripts, Tutorials and Applications / 1d DOS script port
« on: January 16, 2012, 10:15 »
Anders,

Will you please port the 1ddos script to newest ATK version? (with example script)

Thank You

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