Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.

Topics - esp

Pages: [1] 2 3 ... 5
If i have a graphene 2 probe device with source, channel drain, there is a requirement to have the electrode repeated in the channel region .. if my electrodes are created n and p type by doping with specific location of Boron and Nitrogen atoms, and I want to show variation, this is a problem .. for example, if i have an electrode, and to dope it, i can add some dopant atoms in particular locations ... now if i want to see the effect of one of these dopant atoms being placed in the wrong location, i cannot do it, because moving one atom, with automatically require that same atom moved in the mirrored section inside the channel ... so .. is there any way around this requirement?

General Questions and Answers / question about bandstructure
« on: March 14, 2013, 03:25 »
I am not sure if I can explain this well but i will try ..

I did some calculations of bandstructure for graphene ribbons .. now to do this i understood that i needed a sort of unit cell, which for GNRs, is a sort of GNR with a very short length, like 2 hex rings long ... now, i wanted to see the change when doped, so i doped the graphene and i can see the bands shift up and down, n type, p type, etc ... now suppose i want to see the effect of variation ... so the idea is, you dope the graphene, but doping with dopant atoms (although not even possible today), assume it is possible at some time, and there is some variation in the position of the atoms ... Now, if  i want to see the bandstructure change not for a short 2 ring section, but for an entire electrode that is longer, then it all flattens out so that there is no more linear dispersion, etc .. so how can i get to what i am looking for, using atk, in a simple way?  

What i want to know is, for example, if doped and no variation gives Ev, Ec, and Ef values of e1, e2, e3, with some variation, how do these energy levels change? This is easy when the length is short, because for example the band edges are still discernable  .. but when it is longer it is hard to tell

Does this make sense?  if not i can try with pictures

General Questions and Answers / Dr. Blom's NEGF Paper
« on: December 19, 2012, 13:17 »
I was looking for a good NEGF paper and came across the usual suspects (Lundstrom, Datta), but then i found a recent paper by Dr. Blom in 2011!  It is a great paper, you guys should check it out.  I do not have the reference in front of me, but wanted to mention it ..

i have an LDOS calculation running on a $12k, 24 core computer with tons of memory .. for over 1 or 2 weeks now ... non converging i think .. currently at step 140 .. it is graphene GNR two probe device with double gate, N=10 wide, only 16nm long ... i really want an LDOS plot .. does this sound out of ordinary?

35Ghz ring oscillator using novel graphene spice models i developed from atomistic simulations using ATK!

basic spice model of GNR TFET inverter circuit using capacitance and IV curve fit to a level 1 spice model .. all obtained from atk!

General Questions and Answers / calcaultions using same nc file
« on: November 14, 2012, 20:39 »
I ran transmission calcs and got a Ids vs Vgs curve like attached

I ran similar curves at different Vds, 0.4, 0.5, 0.6 ... all using same nc file, and always saving to same nc when done .. then i went back to the 0.5V vds versiob

Now I am seeing something very strange ... i ran a Vds sweep at a fixed Vgs, as attached:

Now I realized I did not take the minimum current point into consideration and I used Vgs = 0.5, which is not what I wanted to do .. so i ran again with Vgs = 0.25 ... but now the results look very odd .. and I am wondering if it has something to do with me using the same nc file every time i calculate ... ?  can the calculations get messed up if starting from the same nc file under many different biases? looks wierd

i have run some simulations and saved some transmission objects there at specific biases .. now i want to run again and use the density calculation, but i need to remove the old transmission objects before i create new ones .. i could overwrite them, but for various reasons i would rather delete them from the file, then continue .. how can i do that? note i want to remove a specific object, not everything ...

General Questions and Answers / p type versus n type
« on: November 10, 2012, 20:38 »
i am having a problem getting a proper IV curve for a p type device ... question .. is there any difference in atk if i have left side source p type, and right side drain n type, and i want to put Vsd = 0.5V .. is there any difference between the following code:

calculator(electrode_voltages=(0.0*Volt, -bias)),




It seems to me there should not be any difference but please confirm ..

then for the gate voltage, if i specify the gate as:

device_configuration.setMetallicRegions([metallic_region0(value = useVgs)] )

where is this referenced to?  I assummed it would be to wherever 0V is, or to some hypothetical ground node somewhere ... can you confirm?  IT seems the voltage you supply here is absolute correct, referenced to some 0V ground node assummed by the system?

General Questions and Answers / memory error?
« on: November 6, 2012, 05:19 »
looks like memory error but i reduced memory steps to 12, and i have never seen one like this ... any ideas?  i was running a electron density calculation on a 16nm long GNR device

patakye@node1083:~/ATKSIMS/shellscripts> head -n 80 msi_runDevTest4.pbs.e439725
/soft/intel/x86_64/12.1/8.273/composer_xe_2011_sp1.8.273/mpirt/bin/intel64/mpirun: line 86: /soft/intel/x86_64/12.1/8.273/composer_xe_2011_sp1.8.273/mpirt/bin/intel64/ No such file or directory
Traceback (most recent call last):
  File "./zipdir/NL/Calculators/", line 291, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 1688, in scfLoopDevice
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 623, in scfLoopDeviceHamiltonian
  File "./zipdir/NL/Calculators/CommonBuilder/", line 461, in createElectrostaticCalculator
  File "./zipdir/NL/CommonConcepts/PoissonSolvers/", line 55, in calculateFunctionOnGrid
Traceback (most recent call last):
  File "./zipdir/NL/Calculators/", line 291, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 1688, in scfLoopDevice
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 623, in scfLoopDeviceHamiltonian
  File "./zipdir/NL/Calculators/CommonBuilder/", line 461, in createElectrostaticCalculator
  File "./zipdir/NL/CommonConcepts/PoissonSolvers/", line 55, in calculateFunctionOnGrid
Traceback (most recent call last):
  File "./zipdir/NL/Calculators/", line 291, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 1688, in scfLoopDevice
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 623, in scfLoopDeviceHamiltonian
  File "./zipdir/NL/Calculators/CommonBuilder/", line 461, in createElectrostaticCalculator
  File "./zipdir/NL/CommonConcepts/PoissonSolvers/", line 55, in calculateFunctionOnGrid

Traceback (most recent call last):
  File "./zipdir/NL/Calculators/", line 291, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 1688, in scfLoopDevice
  File "./zipdir/NL/Calculators/LCAOCalculator/", line 623, in scfLoopDeviceHamiltonian
  File "./zipdir/NL/Calculators/CommonBuilder/", line 461, in createElectrostaticCalculator
  File "./zipdir/NL/CommonConcepts/PoissonSolvers/", line 55, in calculateFunctionOnGrid
*** glibc detected *** /home/it1/patakye/QuantumWise/atk-12.2.2/atkpython/bin/atkpython_exec: double free or corruption (fasttop): 0x00007f05e0002430 ***
======= Backtrace: =========
======= Memory map: ========
00400000-00401000 r-xp 00000000 00:17 6374573                            /home/it1/patakye/QuantumWise/atk-12.2.2/atkpython/bin/atkpython_exec
00500000-00501000 rw-p 00000000 00:17 6374573                            /home/it1/patakye/QuantumWise/atk-12.2.2/atkpython/bin/atkpython_exec
00f81000-0be90000 rw-p 00000000 00:00 0                                  [heap]
7f0543769000-7f05dc000000 rw-p 00000000 00:00 0
7f05dc000000-7f05dc2f2000 rw-p 00000000 00:00 0
7f05dc2f2000-7f05e0000000 ---p 00000000 00:00 0
7f05e0000000-7f05e0021000 rw-p 00000000 00:00 0
7f05e0021000-7f05e4000000 ---p 00000000 00:00 0
7f05e4000000-7f05e42f0000 rw-p 00000000 00:00 0
7f05e42f0000-7f05e8000000 ---p 00000000 00:00 0
7f05e8000000-7f05e82eb000 rw-p 00000000 00:00 0
7f05e82eb000-7f05ec000000 ---p 00000000 00:00 0
7f05ec000000-7f05ec270000 rw-p 00000000 00:00 0
7f05ec270000-7f05f0000000 ---p 00000000 00:00 0
7f05f0000000-7f05f02f0000 rw-p 00000000 00:00 0
7f05f02f0000-7f05f4000000 ---p 00000000 00:00 0
7f05f4000000-7f05f42f0000 rw-p 00000000 00:00 0
7f05f42f0000-7f05f8000000 ---p 00000000 00:00 0
7f05f8000000-7f05f8270000 rw-p 00000000 00:00 0
7f05f8270000-7f05fc000000 ---p 00000000 00:00 0
7f05fc000000-7f05fc021000 rw-p 00000000 00:00 0
7f05fc021000-7f0600000000 ---p 00000000 00:00 0
7f0604c5d000-7f0604c5e000 ---p 00000000 00:00 0
7f0604c5e000-7f060505e000 rwxp 00000000 00:00 0
7f060505e000-7f060505f000 ---p 00000000 00:00 0
7f060505f000-7f060545f000 rwxp 00000000 00:00 0
7f060545f000-7f0605460000 ---p 00000000 00:00 0
7f0605460000-7f0605860000 rwxp 00000000 00:00 0
7f0605860000-7f0605861000 ---p 00000000 00:00 0

General Questions and Answers / total energy
« on: November 1, 2012, 11:36 »
i would like to calculate the total energy for a few configurations .. is this a long calculation or relatively fast? compared to a transmission calc

General Questions and Answers / jumpy curves
« on: October 31, 2012, 09:55 »
I ran a transmission calc for some time, covering some vgs points at one vds value ... the curve was very smooth .. i then restarted the job, to fill in some points, for example near the lowest current point .. the resulting new points made the curve very "jumpy" or unsmooth .. so my question is, is this somehow a function of the fact that I restarted the calculation, or is it really physical?  For example, suppose the current values are 1,2,3 at voltages 0.1, 0.2, 0.3, then I add another point at voltage 0.25, and the current comes out 1.8 ... this is the sort of thing I am talking about, ... I need to know if it is simply because I stopped the calculation and started again, or if i should consider those new points as valid as the original ones .. in other words, is there some history that atk needs when restarting a calculation?  I did in fact load the initial state properly, so i thought i was doing everything right, .. but since this was the first time i got a nice smooth curve, i was dissapointed that the new points from the new job ruined it .... what is happenning? thank you

Future Releases / timestamps
« on: October 31, 2012, 05:31 »
it would be nice if there were timestamps on each step in the iterative algorithm ... i have a job running for a couple days, i can see it is converging around 20 steps per calculation, but i have no timestamp on each step, so i have to grep my log, count the number of steps, and make an estimate .. too much work ... at least if i knew, for example, it seems to be converging at 20 steps, and each step takes 20 minutes, then i can make some sort of rough estimate based on those assumptions, how long it will continue to run for ...

although i am sure we all (including you) would love for calculations to run in minutes, my experience is that I have to plan my entire week around what i have running and when they might finish .. this is a reality of doing this type of simulation .. i have a tfet tansmission calc running for over 3 days, for example ... will it be another 3 days? or a few more hours? i have no idea until a few transmission calcs are done, and i get a timestamp on those ... until then i am in the dark unless i make my own estimates

i seem to be coming up with a lot of non converging graphene tfet devices .. i am tired of retsarting my jobs ... the thing is it happens only for some bias values .. is there a way to specify a max iteration limit so it can just move on to the next bias?  another question is, what will happen if it does not converge, will it just run forever ?  i have a job running now at step 70, about 9 hours ... i dont want to kill it, but i dont know how long it will go on ... what can i do?

Future Releases / free viewers
« on: October 27, 2012, 19:41 »
it would be nice to have some simple viewers, to be able to view geometry for example, if i have 1 vnl license, and i want to send a geometry to my professor to view, i have to make a bunch of screenshots, etc ... a simple viewer would be nice

well maybe my professor would rather see a couple screenshots, but at least for me it would be easier to be able to open up old geometries i used in past simulations, for example, without having to open vnl, which can be slow

for example i double click on an nc file with geometry and it open a simple viewer

General Questions and Answers / how to get object_ids?
« on: October 25, 2012, 02:57 »
i have a set of transmission calcs saved to a file with object_ids that have specific voltages ... how can i get a list of object_ids saved in a file?

Pages: [1] 2 3 ... 5