Topics

1

General Questions and Answers / lddos calculation using GGA

« on: May 16, 2013, 20:48 »

Hi,

I am currently working on the calculation of a 2D MoS2 device. As Ander's recommendation, in my script I first do a geometry optimization before calculating the lddos. And I tried to use GGA for the calculation. The program aborted and I checked the log and I see a non convergence in the simulation and the error message is shown below. I suspect that is because I am using quasi newton for the optimization and I am wondering how I should change the restricts. I am also thinking that for a device simulation if it is proper to use 11 k-point sampling and 60 Hartree as pseudo potential since that will be very time-consuming. The settings worked pretty well for the lattice simulation with just the basis of A moly atom and a sulfur atom but it is not working for the device. Can I know what can I do to modify the script to have the simulation well set? Thank you.
 File "/home/koesters/suxxx172/suxxx172//ATKSIMS/shellscripts/20130505_lddos.py", line 488, in <module>
    optimizer_method=QuasiNewton(),
  File "./zipdir/NL/Dynamics/Optimization/OptimizeGeometry.py", line 229, in OptimizeGeometry
  File "./zipdir/NL/Dynamics/Optimization/OptimizeGeometry.py", line 338, in runSimultaneousRelaxation
  File "./zipdir/NL/Dynamics/Optimization/OptimizeGeometry.py", line 263, in runRelaxation
  File "./zipdir/NL/Dynamics/ASEAtomsInterface.py", line 173, in get_forces
  File "./zipdir/NL/Dynamics/ASEAtomsInterface.py", line 97, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/FastEnergyForcesStress.py", line 28, in energyFunction
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/FastEnergyForcesStress.py", line 65, in _checkAndUpdate
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/FastEnergyForcesStress.py", line 90, in _update
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/EnergyForcesStress.py", line 72, in calculateLCAOEnergyForcesStress
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/EnergyForcesStressUtilities.py", line 19, in setupLCAOEnergyForcesStressCalculator
  File "./zipdir/NL/Calculators/LCAOCalculator/Analysis/EnergyForcesStressUtilities.py", line 344, in setupBackengineConstraints
NL.ComputerScienceUtilities.Exceptions.NLValueError: Stress can only be calculated in the z-direction for devices.
 

2

General Questions and Answers / k-points and periodic boundary conditions

« on: January 8, 2013, 20:05 »

Hi.. I did a new simulation with trying to calculate a periodic ribbon, and I am still using periodic boundary conditions in the y direction. But it never finished. Is there some problem with the periodic boundary conditions I was using? I got the py file attached. Thank you very much.

3

General Questions and Answers / gate scan can not be finished

« on: December 7, 2012, 01:26 »

Hello, I am running a gate scan of a MOSFET to plot the Id vs Vg curve of it. First I calculated the device configuration and transmission spectrum at equilibrium. And then I use the analysis from file to do a gate scan from -2V to 2V. the equilibrium transmission spectrum take like 5 hours to finish, but the gate scan has been running for 24 hours and just complete 2 points. Can you take a look at my script and help me to figure it out? Thank you very much.

4

General Questions and Answers / k-points and periodic boundary conditions

« on: November 29, 2012, 07:42 »

I am kind of confused...The boundary conditions are set by determining the k points sampling right? What does the k-point sampling mean in both electrode and transmission spectrum part? My understanding is that if I set the k-point sampling to be 1 in a direction, in that direction the calculation will be infinite...

5

General Questions and Answers / a single localDeviceDOS simulation took forever to run

« on: October 15, 2012, 00:52 »

Hi

I tried to run a single local device DOS simulation which involves around 200 atom on a super computing machine and I set the walltime to be 48hrs. However, it took the entire 48 hrs and still did not finish. I hope it did converge but I am not sure. Can you take a look at my script and tell me what is the problem? Thank you very much

6

General Questions and Answers / how can I make a device periodical in one direction

« on: September 6, 2012, 01:40 »

Hi all,

I am making a 2d FET device and what I care is just the transporting direction and the vertical direction. How can I make the other direction infinite using periodic boundary conditions and k-point sampling? Should I specify that in the builder or calculator? I wanna save some simulation time by doing that. By the way, If I wanna specify my contacts as gold. Should I just use spacial region in the builder of I need to actually add gold atoms at the contact area? Thank you so much.

7

General Questions and Answers / Can someone give me ideas on how to make a basic FDSOI device?

« on: August 9, 2012, 06:25 »

Hi everyone,

I am a PhD student and I am pretty new to this software. My research involves mainly device simulations and I wish I can start with the most basic device like FDSOIs. I have gone through the builder tutorial but none of them talks about devices so I am totally puzzled. Can you please give me some ideas on how to make the device or are there any tutorials regarding that? I am pretty new and so no background of me can be expected. I am currently using the GUI mode in windows now. Thank you very much.