QuantumATK Forum
QuantumATK => General Questions and Answers => Topic started by: haroon on May 26, 2020, 16:50
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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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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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Can you please explain the difference between 'I-V Curve' and 'I-V Characteristics'?
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It is same. IVCharacteristics can plot the IV curve. We recommend to use IVCharacteristics.
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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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Thank you so much for the response.
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I-V Curve can show spin up and spin down currents separately for spin polarized calculations. Is it possible with I-V characteristics? because it shows me just one current even for spin polarized calculations.
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You must be able to compute the spin up and down components of the current using the Transmission Spectrum (computed in the study object) as described in the manual, see an example of current calculation at https://docs.quantumatk.com/manual/Types/TransmissionSpectrum/TransmissionSpectrum.html.
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OK. Yes I know how to do that. Thanks for the response.