QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: lknife on June 4, 2017, 05:48

Title: How to get the electron affinity from the band structure?
Post by: lknife on June 4, 2017, 05:48

Dear experts,

I want to extract the electron affinity from the band structure where the electron affinity is defined as the difference between the minimum energy of the conduction band (CBM) and free electron level in vacuum. Can anybody here tell me how to do it?

Thank a lot for your time and kind help!

Title: Re: How to get the electron affinity from the band structure?
Post by: lknife on June 4, 2017, 05:54

I had thought that: Since I can get the exact value of Fermi level from the band structure using "text representation", I can calculate the exact value of the CBM according to the exact Fermi level. However, when I did so, it seemed not really the case.

Is anything wrong with my method? Can I get the electron affinity from the band structure?

Thanks for you time and kind help!

Title: Re: How to get the electron affinity from the band structure?
Post by: Petr Khomyakov on June 4, 2017, 13:19

It is impossible to calculate the electron affinity as well as work function just from the band structure. You should create a surface and calculate the conduction band energy minimum with respect to the vacuum level, which is given by the macroscopic in-plane averaged effective potential (there is an analysis object for this potential in the ATK). This energy is then the electron affinity. Note that the electron affinity depends on the surface type chosen; this is similar to work function calculations, where the work function is a property of the surface.

Title: Re: How to get the electron affinity from the band structure?
Post by: lknife on June 5, 2017, 04:07

The system I am now studying is a monolayer, thus it's no need to create a surface. I have calculated the band structure of it and got the conduction band energy minimum (CBM). For example, if the Fermi level of this monolayer is -4.26eV with respect to the vacuum level, I can get the CBM from the band structure.  Is it right?

Btw, which object is for the in-plane averaged effective potential? Is it the "effective potential"? I have never used it before.

Thank you very much for your reply and kind help!

Title: Re: How to get the electron affinity from the band structure?
Post by: Daniele Stradi on June 5, 2017, 12:40

Yes, it is correct, you have to add the difference between the CBM and the Fermi energy to calculate the electron affinity.
An example of how to use the planar average of the effective potential can be found here:
http://docs.quantumwise.com/tutorials/work_function_tuning/work_function_tuning.html

Title: Re: How to get the electron affinity from the band structure?
Post by: lknife on June 5, 2017, 18:25

Thank you very much for your kind help!