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Messages - Petr Khomyakov

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Questions and Answers / Re: Li+
« on: July 19, 2019, 15:07 »
I guess it is technically possible for any element of the Periodic Table, including Li atoms. The question is whether doped Li is representative for Li+ in the particular study of interest, which is not described in the original post.

Questions and Answers / Re: Submit Bug
« on: July 18, 2019, 13:15 »
Please could you send your description of the bug together with the python scripts (and related log files) you used for computing fat band structures in QATK-2018 and 2019  to Thank you.

For modeling a single CNT, you should use a single (Gamma) k-point in the lateral directions, and check if the results converge with respect to vacuum padding thickness.

It is required to accurately compute the Fermi energy in the electrodes. It is impossible to say exactly how many points you need, as it is a matter of convergence tests. Typically, if you have convergence issues with SCF device calculation, one of the possible reasons for that is inaccurately-computed Fermi level. In general, one should also converge the k-point sampling in the lateral directions as well - for CNT, that would just mean that you should have sufficiently thick vacuum padding around the tube to avoid spurious interaction between periodic images of CNT.

For license issues, please send your request to

Please upload log files related to the calculations as well.  Note that 2016.4 is no longer supported version.

Questions and Answers / Re: SET
« on: July 10, 2019, 15:16 »
There is no standard feature of doing it for a single-electron transistor, as QuantumATK considers the electron transport in the coherent regime, dealing with single electron wave functions, not with sequential tunneling. I think you should first decide on the model you want to use for SET, and then see if the parameters of that model can be computed in QuantumATK in one way or the other.

It is hard to say anything without seeing your scripts and logs, and knowing what exactly you have done to get those IV objects. What version of QuantumATK are you using?

Your issue might be related to a bug in computing transmission from bulk configuration calculations. We are currently investigating this. I suggest doing transmission calculations using device configuration (even for perfect bulk material) to avoid any issues. 

Which version of QuantumATK are you using?

Yes, that is correct.

Transmission coefficient is unitless physical quantity, and it is computed per lateral unit cell of the scattering region, i.e., if you, for instance, double the lateral unit cell size in your transport calculations, the transmission will then increase by factor of 2. 

In the Landauer-Buttiker formalism for the electron transport, total transmission can also be seen as conductance in units of G_0,       

DOS is given in # of states per eV (per unit cell, not unit cell area). Integration of DOS  x Fermi-Dirac distribution (at a given temperature and Fermi energy) over the  energy should  give you the number of electrons (per unit cell) in the system.   

Questions and Answers / Re: electrode not perfect
« on: July 9, 2019, 09:40 »
That is totally up to you how to build it. I believe there is no way of making perfect periodic cone without breaking it - this is what QATK did for you. If you want a smooth transition between the scattering/central region and the electrodes, you have to decide on what kind of electrodes you want to attach to the central region. 

Questions and Answers / Re: electrode not perfect
« on: July 8, 2019, 21:48 »
Perfect electrode means periodic electrode, so that you will have to attach a semiinfinite periodic structure to your carbon cones on the left and right side of the point contact to be able to build a device configuration. 

The oldest version that is currently available for download at is 2017.12. Unfortunately, version 2016.4 is no longer distributed. You may request a free trial version of recent QuantumATK 2019.03-SP1 at

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