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To add on the IV-curve analysis object vs. IVCharacteristics study object, the latter is a study object (not an analysis object), meaning that it allows doing many things that the IV curve analysis object would not, e.g., restarting calculations from the point where it was stopped (if job crashed or stopped intentionally), adding or removing (V_ds, V_gs) points, calculating physical quantities (transmission spectrum, potentials, electron density, density of states and so) directly in the study object, and many other things. 

One thing where the IV curve analysis object might be of use is if for whatever reason one wants to independently set the left and right electrode potentials with respect to a common reference when applying a bias voltage, which is a difference between the left and right potentials. In the  IVCharacteristics study object, the right electrode is grounded, i.e., the potential is set to zero by default (at the moment it is not possible to change this default in the study object settings), and the actual bias voltage is applied by changing the left electrode potential. That makes no difference for devices without gate electrodes, but for devices with gates it is important to be aware of this difference between the IVCurve and IVCharacteristics objects.
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I have developed a potential and the potential parameteres are stored in "library.rfmeam.XY" format file. I want to read this file format in quantumatk. How can I read this kind of file ?
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Questions and Answers / Re: Calculation of IV-curves in Quantumwise
« Last post by mlee on May 28, 2020, 23:25 »
It is same. IVCharacteristics can plot the IV curve. We recommend to use IVCharacteristics.
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Can you please explain the difference between 'I-V Curve' and 'I-V Characteristics'?
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Dear Sir

I want to model graphene with hydroxyl group (oh-) and adsorb metal ion how the charge is being implemented on system means first i have to model the oh- ion then adsorb it on the sheet and then model metal ion and adsorb it on the oh- adsorbed sheet is it correct way of modelling the charged system or we need to put charges during optimization of the system.

if charges need to put during optimization of the system then what i need to do, should i need to put resultant charge on the system
for example: lets say
                                  charge on OH = -1 e
                                  charge on metal ion= +3e
    then for modelling metal ion adsorption on oh- adsorbed graphene, +2e should be given in the charge box in calculator to model metal ion adsorbed oh- adsorbed graphene
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Dear all,

 I am attempting to repeat the result of the example  of piezo_GaAs.py (in Page 723 of Reference-Manual, Release 2017.2). Below is my result with 2017.2 version QATK:
"
+------------------------------------------------------------------------------+
| Piezoelectric Tensor Report                                                  |
+------------------------------------------------------------------------------+
|                                                                              |
| Tensor in units of [C/m**2]:                                                 |
|                                                                              |
|           x              y              z                                    |
| xx    4.05800e-01    9.68754e-01    1.02461e+00                              |
| yy    1.67280e-01   -2.57980e+00    1.91885e+00                              |
| zz    1.46679e+00    1.32262e-01    5.77928e-01                              |
| yz   -1.71568e+00    9.27315e-03    9.77441e-03                              |
| xz    9.27315e-03   -9.92013e-01    9.27315e-03                              |
| xy    9.77441e-03    9.27315e-03   -1.43153e+00                              |
|                                                                              |
+------------------------------------------------------------------------------+
"
And this is the result in Page 273:
"
+------------------------------------------------------------------------------+
| Piezoelectric Tensor Report |
+------------------------------------------------------------------------------+
| |
| Tensor in units of [C/m**2]: |
| |
| x y z |
| xx 2.01774e-12    1.27223e-12    1.18732e-12 |
| yy 2.86045e-13   7.92764e-13   5.13819e-13 |
| zz 9.78384e-13   4.45648e-13  -2.59427e-13 |
| yz -8.28198e-01  1.48791e-13  -9.55916e-14 |
| xz 1.17508e-13     -8.28198e-01   7.05227e-14 |
| xy 1.28983e-13      3.64354e-14   -8.28198e-01 |
| |
+------------------------------------------------------------------------------+
"
You can see that they are totally different!!! So, what's wrong?
I appreciate your help! Thanks.
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Questions and Answers / Re: Calculation of IV-curves in Quantumwise
« Last post by mlee on May 26, 2020, 22:53 »
The DFT-LCAO can calculate the device using the NEGF.

If you look at the below linked tutorial, you can see the IV curve in Si device using the DFT-LCAO vs. DFT-semi-empirical method   
https://docs.quantumatk.com/tutorials/silicon_pn_junction/silicon_pn_junction.html

Recent version implements the IVCharacteristics GUI in the study object.
https://docs.quantumatk.com/tutorials/ivcharacteristics/ivcharacteristics.html
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Questions and Answers / Calculation of IV-curves in Quantumwise
« Last post by haroon on May 26, 2020, 16:50 »
Dear Friends,
Can we use DFT:LCAO(Device) Calculator for the calculation of IV-curves in Quantumwise? If not then which one should be used?
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Regarding computing DOS for graphene see Appendix in Phys. Rev. B 87, 075414 – Published 7 February 2013. As Tue suggested also try increasing the number of k-points significantly. Did you also use tetrahedron method with significantly increased k-point density? It would also be helpful to see your script.
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This is exactly what my previous post is about that one can define the physical position of the Fermi level when using the Fermi Dirac broadening method available in QuantumATK for DFT calculations for a given electronic temperature, which acts a broadening/smearing parameter in SCF electronic structure calculations, see the manual https://docs.quantumatk.com/manual/Types/FermiDirac/FermiDirac.html for more details.
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