Recent Posts

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21
General Questions and Answers / capacitance of the MOSFET
« Last post by wisam on December 7, 2021, 22:17 »
Hello Quantum ATK users
Please guide me to get the total capacitance of the MOSFET?
22
General Questions and Answers / Re: Polyimide not available in database
« Last post by BradWells on December 7, 2021, 09:34 »
Hi Par_Navidi,

In QuantumATK, you are able to build and import your own monomers into the Monomer Database.  In this case you can build a monomer of kapton in the builder.  Remember to tag the head and tail atoms so that the Polymer Builder knows how to connect the monomers to form a chain.  Using the imported monomer you should be able to use the Polymer Builder to create a 3D amorphous structure of kapton. If your material is crystalline and you know the crystal structure, you can also import CIF files into the Builder.

With respect to the thin film part of your problem, the Polymer Builder packs polymer chains into the simulation cell with isotropic orientations.  It currently doesn't support aligning the polymer chains along a particular axis.  On the scale of atomic simulation 20nm is quite large, so it may be necessary to consider the material as continuous in all directions and then apply stress in particular directions.

Cheers,
Brad.
23
On December 6, 2021, we have released a Service Pack QuantumATK S-2021.06-SP2 (bugfix update).

If you are a customer entitled to maintenance services, you can access QuantumATK S-2021.06-SP2 and download release notes directly from SolvNetPlus.

Find more information about  the main QuantumATK S-2021.06 release here.
24
General Questions and Answers / Re: Time-dependent DFT and photoluminescence
« Last post by mlee on December 6, 2021, 09:46 »
Regarding to the TD-DFT, QuantumATK doesn't have it.
25
General Questions and Answers / Re: Polyimide not available in database
« Last post by mlee on December 6, 2021, 09:45 »
The below link will guide how to build the polymer.
https://docs.quantumatk.com/tutorials/polymer_builder/polymer_builder.html
26
General Questions and Answers / Polyimide not available in database
« Last post by Par_Navidi on December 5, 2021, 22:44 »
I would like to determine the resistivity of the 2D polyimide (kapton) thin film as a function of the applied stress and induced defects. I have the following problems:
1) I can not find the 3D structure of the polyimide in the database. I was only able to find a 2D structure at some websites…How can we have access to such chemical structures?
2) for a 20 nm-thick thin film of polyimide (50 layers of polymer) how I should consider the orientation of the polymer chains in the confined direction? Does the interactions changes the resistivity of the material?
27
General Questions and Answers / Time-dependent DFT and photoluminescence
« Last post by hadhemat on December 1, 2021, 10:19 »

Hello,

I am trying to calculate photoluminescence spectra for my structures by ATK. I guess I have to do time-dependent DFT. Is TD-DFT implemented in ATK? If yes, how can I use it? If no, is there another way to calculate photoluminescence spectra by ATK? Thanks

Hadi
28
General Questions and Answers / Re: Charge transfer
« Last post by Petr Khomyakov on November 25, 2021, 15:42 »
You might consider using the Bader analysis instead of Mulliken population, see https://docs.quantumatk.com/manual/Types/BaderCharges/BaderCharges.html and reference therein.

Another way is based on the electron density analysis, as described, e.g., in this paper First-principles study of the dipole layer formation at metal-organic interfaces, Paul C. Rusu, Gianluca Giovannetti, Christ Weijtens, Reinder Coehoorn, and Geert Brocks
Phys. Rev. B 81, 125403 – Published 3 March 2010.
29
General Questions and Answers / Computing surface energies
« Last post by Weckman on November 24, 2021, 22:20 »
I would like to study the stability of different surface orientations of wurtzite/zinc blende materials which exhibit asymmetric surfaces for certain lattice orientations and therefore would like to use the periodic surface model (electrode) to compute the relative stabilities of these surfaces.

I do not yet have the full licence in my disposal, so I ran some test calculations on my desktop for Au(111) surface. However, when I compute the total energy of surfaces with varying thickness, in some instances I get negative surface energies.

For example, when using surfaces with 6 and 8 layers of gold, medium basis set and SG15 pseudo, I get energies
6   -22519.98379
7   -26273.25555
8   -30026.51107
Making a linear fit gives a slope of -3751.264 eV, close to that of a bulk calculation (-3753.231 eV). However, the intercept is negative and so is the surface energy.

If I use a HGH pseudo, I get a positive surface energies that vary depending on the basis set used.

What I would like to know:
Is this a correct approach to take and are the results some kind of an artifact resulting from a thin surface model or am I making a fundamental error somewhere or how should I approach the issue? In the original paper ("First-principles Green’s-function method for surface calculations: A pseudopotential localized basis set approach") the authors discuss developing the procedure for SG15 pseudos. However, QuantumATK allows me to set from a variety of different pseudos. Is the Green's function method suitable for all the available pseudos and basis sets?

- Weckman

30
General Questions and Answers / Charge transfer
« Last post by khariyahA on November 24, 2021, 20:21 »
Hi Sir,

Im currently studying about GNR for gas sensor. I have difficulty in interpreting and calculate charge transfer from mulliken population result.

I really need help and i appreciate any advice regarding this. Thankyou :)
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