Messages

1

General Questions and Answers / why current is different at the same voltage?

« on: June 29, 2012, 17:16 »

Dear all:
       Now I am facing a new problem like this, I hope you can give some help:
       When I calculated the I-V character of Au-Si two probe system in many different voltages, I set the voltages using the following fomat:
       for voltage in numpy.linspace(0.0,2.0,10)*Volt
       And then, I got the currents at every voltage points.
       However, if I set the voltages separately, that is I calculated one current in relevant voltage a time, I got another current value, this current is much smaller than the previous one at the same voltage. For example, at the given voltage of 1.8V, calculated in [for voltage in numpy.linspace(0.0,2.0,10)*Volt], the current is about 120000nA, calculated with only one point voltage at one time, the currrent is about 25000nA, the latter one is much smaller. Why do this happen? This puzzle me a lot.
      Additional, did the direct of applied voltage in electrode have some effect on current magnitude, or it just affect the current direct?
     Thank you for your reply.
     Sincerely, lida.

2

General Questions and Answers / Re: run error, please help

« on: June 5, 2012, 10:58 »

okay, I got it. Indeed, the checkpoint file have already exist in my directory which I ignored when doing the calculation. Thanks a lot for your helpful reply.

3

General Questions and Answers / run error, please help

« on: June 4, 2012, 13:27 »

Dear everyone，
I am a newcomer in ATK using, when I calculated the transmission spectrum of Au-Si two-probe system, I encountered the problem like this:
error message:
Traceback (most recent call last):
  File ".\zipdir\NL\Calculators\DeviceCalculatorInterface.py", line 257, in _update
  File ".\zipdir\NL\Calculators\LCAOCalculator\LCAOCalculator.py", line 1092, in scfLoop
  File ".\zipdir\NL\Calculators\LCAOCalculator\LCAOCalculator.py", line 799, in scfLoopHamiltonian
  File ".\zipdir\NL\Calculators\GenericParameters\CheckpointHandler.py", line 131, in _storeIfNecessary
  File ".\zipdir\NL\IO\IOUtilityFunctions.py", line 1142, in setupForOverwrite
  File ".\zipdir\NL\IO\MetaCDFFile.py", line 241, in __init__
  File ".\zipdir\NL\IO\MetaCDFFile.py", line 891, in _read
  File ".\zipdir\NL\IO\MetaCDFFile.py", line 977, in _readVariables
NLIOError: Error: unexpected header encountered when reading variables
I am not sure what is wrong, is there any problem in device structure or calculation script?
Another question, in my calculation script, where can the checkpointfile statements locate?
In addtion, I run atk_windows_32bit in my 64bit OS with 4Gb memory, whether the program only use 2Gb memory like in 32bit OS?
The following is my script. Thank you very much for your help.