Topics

1

General Questions and Answers / The computation failed to converge when the negative bias was applied

« on: November 30, 2010, 14:02 »

Hi. everyone!
Hi, Blom! I have also tried to search the forum for the topics similar to the following problem but there are no findings. Sorry! 

I am calculating a two-probe system using 2008.10 version. The I-V characteristic under the positive bias has been computed successfully and effortlessly. However, the computation is very difficult to converge when the negative bias is applied on the system. Then I changed the electron temperature from 300K to 500K, and the problem was still existing. Can anyone tell me what is the reason and how can I do to solve the problem? Thanks in advance!

2

General Questions and Answers / Is it reasonable that the current is different?

« on: September 10, 2009, 07:55 »

  Hello!
  A question again. 
  When I run I-V calculation, I found it was hard to converge under high bias after many steps. The electrode temperature is 300k. I think the current should not be zero, even if the job can converge, because the charge in the logwindow keeps large. For the convergence problem, I stoped the calculation. Then I changed the electrode temperature to 1000K and re-calculated the current. The task terminated normally in a short time and the current is close to zero. It is all close to zero though the temperature is changed to 500K or 400K. So I confused very much. Which result can be believed?  Is it reasonable that the current has different value apparentlly under different temerature or other conditions?

  Thanks in advance!

3

General Questions and Answers / should I run SCF calculation separately under various method parameters?

« on: September 9, 2009, 17:01 »

Hello all!
I want to compare the difference of the zero bias transmission spectrum(TS) under various method parameters, for example K-point samping. The SCF calculation with specific K-point(1x1x500) has been executed and I used it to run the corresponding TS. Then I change K point to another one. Should I re-calculate zero bias SCF in this K-point setup firstly before the new TS calculation will start?
In other words, is the zero bias SCF result in specific parameters always useable for all analysis calculation even one has changed the method parameters?
One more question, in the case above mentioned, should the K-point be samed in "method" with in "analysis" when one calculates TS? I know the post "About the Number of k-points ?" in this forum, but I am still confused a bit.  Which one can bring more effect on the transmission results? 
Best regards!

4

General Questions and Answers / A question about MPSH calculation：some eigenstates can't be obtained

« on: August 31, 2009, 06:55 »

Hello,everyone. 
I found that my probe-system calculation can terminated normally when the quantity of the MPSH eigenstates was less than 17, however, can not terminated normally when the quantity was 18 or larger.  In the case of the latter, the *.vnl file can still plot normally in the Nanoscope but there are only 17(index from 0 to 16) eigenstates, and other eigenstates above the 17th can't present in the nanoscope list.  The error message in the output log is as below:

Traceback (most recent call last):
  File "c:/docume~1/admini~1/locals~1/temp/tmpb12hgk.nl", line 298, in ?
    if processIsMaster(): file.addToSample(state, 'MPSH 2.0V', label)
MemoryError:
Terminated Abnormally

Can anyone tell me the reason? And how can I solve the problem? Thanks in advance!

5

General Questions and Answers / two "0" values in the calculation result of MPSH energy spectrum. Why?

« on: August 25, 2009, 05:52 »

hello, fellows! this is my first post here:)
A problem. After I performed the calculation of MPSH energy spectrum under a specify bias in my probe system, I found there are two "0 eV" values in the export result.  what is the reason? and what it means
thanks in advance!