QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: jerry on July 1, 2011, 04:01

Title: device calculation
Post by: jerry on July 1, 2011, 04:01

Dear everyone
    I a newcomer on ATK. I have several questions that confused me.
    (1) Does the DOS calculation for a two probe or three probe system  represent the central region of thses systems?
    (2) How to determine the quantum numbers in the eigenstates in the calculation?
   Thank you very much!!!

Title: Re: device calculation
Post by: kstokbro on July 1, 2011, 11:02

1. The DOS is for the central region, you can also project into individual atoms using the PDOS interface to the dos. You enter the PDOS interface by selecting PDOS plot when you have selected the DOS object in the result browser.

2. I assume you are refering to the transmission eigenstates?
quantum_number=0, is usually the most important eigenstate, it is the one that carry the most of the transmission. You can calculate the transmission eigenvalue for each quantum number using the function, TransmissionEigenvalues

Title: Re: device calculation
Post by: jerry on July 4, 2011, 05:28

Thank you very much for your kind reply. Do you mean that I should first calculate the eigenvalues of different quantum numbers and then to decide which eigenstate to calculate? I can not figure out what do the quantum numbers mean.
Thank you again!

Title: Re: device calculation
Post by: zh on July 4, 2011, 12:10

Roughly, the "quantum numbers" in the calculations of "transmission eigenstates"  are the index for the transmission eigenvalues or the transmission channel. Since the transmission coefficient at a given E and k is decomposed into "TransmissionEigenvalues", one can find out the largest contributions to the transmission coefficient from the calculated transmission eigenvalues. The analysis of the transmission eigenstates with largest contributions to the transmission coefficient will be more interesting.

Title: Re: device calculation
Post by: jerry on July 14, 2011, 10:36

Thanks a lot :)
I also have several questions.
(1) How to calculate the HOMO and LUMO of a single molecule? I mean the wavefunctions.
(2) Is the central region in a device configuration periodic along x and y axis?
   

Title: Re: device calculation
Post by: zh on July 14, 2011, 12:53

For the first question, it is quite simple. The wavefunction of molecular levels can be obtained by calling "Eigenstate()", please refer to the manual:
http://quantumwise.com/documents/manuals/latest/ReferenceManual/index.html/ref.eigenstate.html

For the 2nd question, the answer is yes.

Title: Re: device calculation
Post by: jerry on July 14, 2011, 14:37

 :)
Thank you!
I have known that the eigenstate function can calculate the HOMO and LUMO, but how to determine the quantum number for the HOMO and LUMO? Can you give me an example?

Title: Re: device calculation
Post by: zh on July 20, 2011, 11:35

For example, a NH3 molecule contains 8 valence electrons. So the first 4 molecular orbitals will be fully occupied by these 8 electrons. In ATK, the index of molecular orbital starts from zero. So the index for the HOMO and LUMO of NH3 will be 3 and 4, respectively.