Topics

1

General Questions and Answers / Molecular Energy Spectrum

« on: March 27, 2015, 08:43 »

Hi,Everyone

Hope you are grand. I have obtained MolecularEnergySpectrum at 0 bias voltage for a MTJ in Parallel Configuration(PC) and the results(and py file) are attached here. I actually intend to calculate HOMO and LUMO energy-level at 0 bias for spin-up and spin-down carriers for this MTJ in PC but I can't seem to understand the results I have got(I hope this is the right way to find HOMO and LUMO). I seek your advice on how to find HOMO and LUMO for spin-up and spin-down carriers from these results and also what do the 3 columns under spin-up(and spin-down) represent. I hope I have provided enough information about my problem and am waiting for someone to address these issues. Have a nice day..!!

2

General Questions and Answers / Change in HOMO-LUMO gap with change in Voltage

« on: March 25, 2015, 06:44 »

Hi, Everyone

I would be grateful if you could help me resolve an issue i am having. I earlier calculated I-V characteristic of a two probe geometry(specifically a MTJ) through Analysis -> I-V curve method for PC and APC. Now I want to find the HOMO-LUMO gap at different bias voltages. Please tell me how i can find this change in HOMO-LUMO gap with the change in bias voltages from above I-V curve result at the earliest. I look forward to your comments. Have a blessed day..!!

3

General Questions and Answers / ATK compatability

« on: February 23, 2015, 11:34 »

Hello,
Everyone

I have one geometry in ATK 2008 with me. However, i also like to use the same geometry in ATK 2014. Is there any way to use the geometry made in ATK 2008 in ATK 2014? If yes then please guide me as to how to go about it? Have a nice day..!!

4

General Questions and Answers / Negative TMR

« on: February 11, 2015, 08:12 »

Hi,

I intend to calculate TMR at diff. bias voltages for a MTJ. Now i read in one paper the TMR equation which is (Ipc-Iapc)/Iapc. Unfortunately in my case Iapc is greater than Ipc at all bias voltages (Am i wrong right here?  )  and hence according to the aforementioned TMR eq. i get negative TMR. So i was wondering if it was justifiable to have negative TMR or i should really tinker the equation a little like (Iapc-Ipc)/Ipc. I am waiting for a comment on this..!!

5

General Questions and Answers / Resuming calculation

« on: December 11, 2014, 11:57 »

Hi, I wanted to calculate I-V characteristic at diff. biases (0,0.1,0.2,....,1.2 V) for a two-terminal device. I was running this simulation on cluster and it,due to some reason, got killed when it was in the middle of the convergence process at the last bias point(1.2 V). Now I have been through one tutorial on this and other posts(most of which pertain to old versions) on this forum and frankly speaking i am a noob in Quantumwise so pardon me if it comes across as very basic stuff. In my log file, it shows Checkpoint file location in tmp folder but when i tried to locate it, i couldn't find it. For the record, it has been 15 days since the job got killed on cluster. So could someone please explain the whole resuming process in a little detail?

6

General Questions and Answers / Transmission Spectrum

« on: November 26, 2014, 12:32 »

Hi

i want to calculate transmission spectrum at different biases for a two terminal device in one go. is it possible and if yes then how?

7

General Questions and Answers / nA and nB sampling points' values

« on: November 26, 2014, 10:08 »

Hi,

I intend to calculate transmission spectrum and IV curve for a FM-semiconductor-FM structure. I am not sure what values should i assign to nA and nB sampling points in the transmission spectrum analysis box. I have gone through similar Fe/Mgo/Fe tutorial and there they have kept nA=nB=1 and i think it is because it's not a 3D structure while my structure is 3D and that's why nA=nB=1 might not be appropriate for a 3D structure. I reckon in my case nA and nB should be 3 since it's a 3D structure. I will appreciate an expert remark on this. Have a nice day..!!

8

General Questions and Answers / Spin current calculation

« on: November 12, 2014, 11:56 »

Hello,

I would like to obtain in total 4 plots, as mentioned below, at different biases for a two terminal structure(FM-Semiconductor-FM).
(1)spin up current in parallel config
(2)spin down current in parallel config
(3)spin up current in anti-parallel config
(4)spin down current in anti-parallel config

I am not sure what is the exact procedure to achieve these results so please advise me on how to set about getting these plots. Any help in this regard will be appreciated.

9

General Questions and Answers / Zero bias TMR

« on: November 12, 2014, 11:29 »

Hello,

I am trying to calculate TMR and Spin- Injection factor(n) for a two terminal device(FM-semiconductor-FM) at different biases. Here TMR is defined as (Ipc-Iapc)/Iapc and n is defined as (Idown - Iup)/(Idown + Iup), where Ipc=total current in parallel config, Iapc=total current in anti-parallel config, Idown=Down spin current and Iup=Up spin current. As we all know at the bias of 0.0V, all currents are zero and hence we gotta use equilibrium conductance and corresponding currents(I know this from one paper) . So my question is how do we calculate this equilibrium conductance and corresponding currents at the bias of 0.0V in Atomistix Toolkit?