Messages

31

General Questions and Answers / Re: No charge value when run the Mulliken population

« on: March 22, 2018, 13:02 »

From your log file it does not appear that you have run a Mulliken Population analysis: You do a non-selfconsistent Huckel calculation, then TotalEnergy, Bandstructure, and DensityOfStates analysis. However, the calculator log shows you that the occupation (DM) on P and N atoms is 5, and on H atoms it is 1.

32

General Questions and Answers / Re: Can anybody help me with the concept "contributions" in tranmissionpathway?

« on: March 15, 2018, 12:59 »

(1) Yes, under forward bias (where the electrons move from right to left) it probably makes good sense for you to do the TransmissionPathways analysis using Right contributions.
(2) As writtin in the ATK Manual, https://docs.quantumwise.com/manuals/Types/TransmissionPathways/TransmissionPathways.html, the method "evaluate()" should give you the data you are looking for. This should also be what the Text Representation gives you. You could also try to nlprint the TransmissionPathways object.
(3) Default electron energy for evaluation the transmission pathways is at the average Fermi level. You may choose a different energy, but be aware that the current-carrying states will in general be the ones in the energy window between the electrode Fermi levels.

33

General Questions and Answers / Re: Device DOS

« on: March 15, 2018, 12:47 »

That is just a technical matter, nothing to worry about. In the case of GGA, the spin components are both exactly identical, so their sum is the relevant one.

34

General Questions and Answers / Re: calculation of capacitance

« on: March 14, 2018, 14:57 »

I agree that the tutorial could explain those details a bit bettoer.
- Accumulated Mulliken charge plot: plots the same as the "Net Mulliken Charge" plot above, but in terms of the accumulated Mulliken charge
- The induced charge is calculated in this line in the analysis script:

Code

# Compute the total induced charge on one surface, defining the first 7 atoms as belonging to the left surface
q = [-numpy.cumsum(c-net_charges[0])[7] for c in net_charges]

so the induced charge is calculated as CummulativeSum([Q_i]), where Q_i is a list of mulliken charge difference on all atoms in the left part of the central region wrt the zero-bias charge .

35

General Questions and Answers / Re: No charge value when run the Mulliken population

« on: March 14, 2018, 14:23 »

Your attachment does not indicate any problems. Please supply a script and a log file that indicates a problem.

36

General Questions and Answers / Re: Can anybody help me with the concept "contributions" in tranmissionpathway?

« on: March 14, 2018, 14:22 »

I think the ATK Manual explains it rather well:  https://docs.quantumwise.com/manuals/Types/TransmissionPathways/TransmissionPathways.html
Default contributions is Left, meaning you study the transmission pathway for electron originating in the left electrode and transmitted to the right electrode. I would say no, you do not need to redo the analysis with contributions=Right.

"Arrows point in the direction of the pathways. The magnitude of the pathway is illustrated by the volume of the arrow and the color shows the direction"

"The local bond contributions, T_ij, can be both positive and negative. A negative value correspond to that the electron is back scattered along the bond. A positive value of T_ij  is visualized as an arrow from i to j, while a negative value is visualized as an arrow from j to i, i.e. the direction of the arrows shows the flow of the electrons.

37

General Questions and Answers / Re: Thermoelectricity as a function of temperature

« on: March 12, 2018, 14:23 »

Small correction to the script I previously attached: For ATK 2017, script line 2 should be

Code

from PyQt4.QtGui import QApplication

38

General Questions and Answers / Re: Thermoelectricity as a function of temperature

« on: March 12, 2018, 12:41 »

Dear Rebeda,

there is actually another (and better) way of doing batch analysis of thermoelectric properties: Use a script that directly interacts with the TransportCoefficients plugin instead of duplicating old code.

I attach a script that does this for the case of T=400 K and a Fermi shift of 0.1 eV. I am sure you can figure out how to adapt it to your specific needs, i.e. implement a loop over temperatures. HINT: if you just want to vary the temperature for one single device (no changes to the electron and phonon bandstructures), implement the loop over temperatures from line 24 and down.

Kind regards,
Jess Wellendorff

39

General Questions and Answers / Re: Geometry optimization under electric field

« on: March 12, 2018, 10:00 »

Yes, I think it can.

40

General Questions and Answers / Re: Looking for a tutorial about the Bi2Se3 thin film device

« on: March 12, 2018, 10:00 »

Just never had the time to finish it.

41

General Questions and Answers / Re: Looking for a tutorial about the Bi2Se3 thin film device

« on: March 6, 2018, 09:01 »

Dear lknife,

we took that Bi2Se3 transport case study offline because it is still not fully finished, possibly even wrong on certain points. However, I have compiled it as HTML for you and zipped it: https://www.dropbox.com/s/krc7h9018ge2imr/bi2se3_transport_case_study.zip?dl=0

After unzipping, you open the file "html/index.html" in your browser in order to see the contents.

Kind regards,
Jess Wellendorff

42

General Questions and Answers / Re: Error regarding the self energies when calculating transmission pathways

« on: March 1, 2018, 15:03 »

We received your email now.

43

General Questions and Answers / Re: Bismuth

« on: March 1, 2018, 15:02 »

A few points:
1) It does not look like you have geometry optimized the nanowire. In the paper you mention, they clearly relax the structure before doing band structure analysis.
2) If you want to consider the band path G -> K, you probably want to convert the lattice from UnitCell to Hexagonal (do that using the Lattice Parameter widget).
3) I think you should use SG15 pseudopotentials instead of OMX, and probably PBE instead of LDA.
4) Also compute the DOS: should clearly indicate if the hydrogen passivation worked as it should (removing spurious states around the Fermi level)
5) As a starting point, don't worry about spin-orbit coupling.

I attach a script that basically does this. Hope it is useful.

BR,
Jess

44

General Questions and Answers / Re: Calculation of Fermi Velocity

« on: March 1, 2018, 14:18 »

Fermi velocity, refer to the ATK Manual https://docs.quantumwise.com/manuals/Types/calculateVelocity/calculateVelocity.html Please see previous Forum posts
https://quantumwise.com/forum/index.php?topic=4960.msg21465#msg21465
https://quantumwise.com/forum/index.php?topic=3337.msg15413#msg15413

As for quantum capcitance, your quesation is a bit vague on the details, but we have a tutorial on atomic-scale capacitance: https://docs.quantumwise.com/tutorials/atomic-scale_capacitance/atomic-scale_capacitance.html

45

General Questions and Answers / Re: Geometry optimization under electric field

« on: February 26, 2018, 09:40 »

Depends on what sort of system you have in mind. If you are thinking of applying a field vertically across a 2D material, we have a tutorial on that: https://docs.quantumwise.com/tutorials/opening_a_band_gap/opening_a_band_gap.html