QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: mantun on July 18, 2014, 04:25

Title: IV curve nan (not a number)
Post by: mantun on July 18, 2014, 04:25

I calculated the IV curve of a two-probe system with voltage ranging from -1V to 1V and found that the current at some voltage is nan (not a number). THe process is obtaining the scf nc files first, then computing the transmission spectrum and finally using the result analysis to get the IV curve. Can you tell me what's the problem?

Title: Re: IV curve nan (not a number)
Post by: mantun on July 22, 2014, 02:36

no offical reply?

Title: Re: IV curve nan (not a number)
Post by: Anders Blom on July 22, 2014, 06:50

More info needed. At the voltage giving problem, what does the transmission spectrum look like? Did all calculations converge? How do you compute the current (which tool - a VNL tool or a script)?

Title: Re: IV curve nan (not a number)
Post by: mantun on July 22, 2014, 08:36

Quote from: Anders Blom on July 22, 2014, 06:50

More info needed. At the voltage giving problem, what does the transmission spectrum look like? Did all calculations converge? How do you compute the current (which tool - a VNL tool or a script)?

The voltage range is -1 to 1 V, several votages give the problem. Even several voltage do give the current, the current is extremly small (about 1e-20 A). I used a loop to abtain the scf result, then a script is employed to compute the transmission spectrum. With the "IV analyzer" in vnl, the current is calculated. Surprising, I don't get the curve of transmission spectrum in the "IV analyzer". I turned to check the scf nc file, only a Warning -"The provided initial state parameter has no pre-calculated data.Proceeding without setting an initial state." -was found.

Title: Re: IV curve nan (not a number)
Post by: Anders Blom on July 23, 2014, 06:08

Screenshots/plots would help, of the transmission and where the current is shown as NaN. Also, an idea of your system, ideally the scripts (by mail if secret).

Title: Re: IV curve nan (not a number)
Post by: mantun on July 24, 2014, 02:40

Quote from: Anders Blom on July 23, 2014, 06:08

Screenshots/plots would help, of the transmission and where the current is shown as NaN. Also, an idea of your system, ideally the scripts (by mail if secret).

i give you the screenshot of I-V curve in the vnl analyzer. Two scripts will be emailed to you. one is used to abtain scf results, and the other one is used to obtain transmission spectrum.

Title: Re: IV curve nan (not a number)
Post by: mantun on July 29, 2014, 04:32

The forum staff think this result from the wrong geometry of two-probe system (that is the electrodes don't recover their bulk properties). But i haven't prove it. After i have done this, i will put my conclusion here.

Title: Re: IV curve nan (not a number)
Post by: Rohit on January 26, 2015, 20:21

Please attach the two scripts which are  used to obtain scf results,and  transmission spectrum.......how can IV cuve be plotted using .nc file results....