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Messages - Daniele Stradi

Pages: 1 ... 17 18 [19] 20
271
General Questions and Answers / Re: Formation of MoS2 Tube in new ATK -2015.1
« on: March 22, 2016, 11:34 »
Dear meena,

could you be more specific on where is the problem. Following step 1 and 2 and using the transformation matrix:
A' = 1, 1, 0
B' = -1, 1, 0
C' = 0,0,1
you should be able to obtain an orthorombic cell.

272
General Questions and Answers / Re: Simulated current-voltage characteristics and extraction of n
« on: March 21, 2016, 10:27 »
You should use the "Left   electrode chemical potential" from the device calculation: -2.820920 eV

273
General Questions and Answers / Re: BZ Routes: K and K-prime
« on: March 17, 2016, 09:40 »
Your procedure is correct, but of course depends on the actual system, and on the program/method used.

 

274
General Questions and Answers / Re: BZ Routes: K and K-prime
« on: March 16, 2016, 10:24 »
Yes, that should work perfectly.

275
General Questions and Answers / Re: analysis of zero bias result of a two probe device
« on: March 15, 2016, 10:15 »
Hi Jenny,

the short answer is yes. Please see the section "k-dependent transmission" in the same tutorial:
https://www.quantumwise.com/documents/tutorials/latest/MolecularDevice/index.html/chap.analysis.html#sect1.analysis.ktransmission

276
General Questions and Answers / Re: Simulated current-voltage characteristics and extraction of n
« on: March 7, 2016, 11:14 »
The density of states can be obtained using the ProjectedLocalDensityOfStates object:
http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.projectedlocaldensityofstates.html

The blue line is the system electrostatic difference potential:
http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.electrostaticdifferencepotential.html

Notice that, to match the conduction band minimum of the semiconductor, the electrostatic difference potential has been shifted by (i) subtracting the chemical potential of the right silicon electrode, that is the silicon electrode and (ii) adding the difference in energy between the conduction band minimum of doped bulk silicon and the Fermi energy.

277
General Questions and Answers / Re: relaxation+spin
« on: February 29, 2016, 11:19 »
Dear Cyrille,

the behavior you observe is due to the fact that a new density matrix has been set up in the new relaxation step.

In the OptimizeGeometry function,

http://www.quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.optimizegeometry.html

there is a parameter called "scf_restart_step_length". The default is set to 0.1 Angstrom. If any atomic displacement between two consecutive optimization steps is larger than this value, a new density matrix will be set up, and the one calculated from the previous geometry will not be used.

 



278
General Questions and Answers / Re: How to construct (ZnO)12 nanocluster
« on: February 29, 2016, 10:47 »
Could you tell us which (ZnO)12 structure are you referring to? Is it the sodalite-like one?

279
General Questions and Answers / Re: building structure
« on: February 29, 2016, 10:13 »
You can import Crystallographic Information File (*.cif) directly into VNL:
http://docs.quantumwise.com/tutorials/vnl_io_import.html

The relevant*.cif file for magnetite can be downloaded from the Crystallography Open Database, for example:
http://www.crystallography.net/cod/1011032.html


280
General Questions and Answers / Re: Simulated current-voltage characteristics and extraction of n
« on: February 29, 2016, 09:43 »
Please refer to this article for the relevant methods and references:
http://arxiv.org/abs/1601.04651

281
General Questions and Answers / Re: Formation of MoS2 Tube in new ATK -2015.1
« on: February 22, 2016, 10:41 »
Hi,

there is an errata in the tutorial you mentioned. Try to follow the steps in the tutorial with these two changes:

- Step2:
The correct matrix is:
A' = 1, 1, 0
B' = -1, 1, 0
C' = 0,0,1

- Step5:
If everything is done correctly you should be able to set the lattice parameters matrix as follows:
A = 65, 0, 0
B = 0, 63.208, 0
C = 0, 0, 5.47397


282
General Questions and Answers / Re: Band to Band tunneling.
« on: February 9, 2016, 11:59 »
Dear Tufan,

you can do it using the NEGF+DFT method implemented in ATK. For example, check this tutorial and the related article in which band-to-band tunnelling is simualted in a InAs p-i-n junction:

http://quantumwise.com/documents/tutorials/latest/InAsDevice/index.html/

http://in4.iue.tuwien.ac.at/pdfs/sispad2013/19-1.pdf

283
General Questions and Answers / Re: Spatial Dielectric/ Metallic Region
« on: February 8, 2016, 09:18 »
With respect to 2): the oscillations are actually there, but the device is so big in this case that they are hard to see :) If you want a "planar" average, you should consider doing a macroscopic average of the electrostatic potential. See http://arxiv.org/abs/1601.04651 and references therein (in particular, Ref. 48).

With respect to the w.f. question: if you set the gate voltage to 0 Volts, that won't affect the band alignment in the system.

284
General Questions and Answers / Re: EIGENVAL files and BandStructure Analyzer
« on: January 14, 2016, 10:42 »
Dear Mark,

Sorry for the late reply. I can reproduce your error (although, with a different VASP output). I agree this should not happen.

Could you try to uncheck the "00" folder in the Project File list, and then check it again? In this way you make sure that VNL reads properly all the files in the folder. In my case, this made the EIGENVAL file appear in the LabFloor.

Notice that the files needed to display the EIGENVAL file in the LabFloor are: EIGENVAL,DOSCAR,KPOINTS

Regards,
Daniele.

285
General Questions and Answers / Re: POSCAR: Import-Export Issues
« on: January 4, 2016, 12:43 »
As far as I can see the "POSCAR-after" file is correctly set up for atomic relaxation. You might want to have a look at the description of POSCAR file in the VASP manual.

- The "T" option means that you allow for relaxation, the corresponding option for fixed atoms is "F".
- If you delete the "T" options, you should also delete the "Selective dynamics" line.

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