[Pw_forum] Electron affinity calculation

[Stefano Baroni]

On Jan 27, 2007, at 8:39 AM, Alexander Shaposhnikov wrote:

Hi Sasha:


> I would like to calculate Electron Affinity in zirconia.
> The simplest idea is to put additional electron in the cell
> and calculate total energy difference.This, however, will not
> work as calculated bands energies and fermi level are not connected
> to vacuum level. So, the energy of the first conductive band, which  
> is a good
> estimation of the electron affinity, is meaningless by itself.

right

> My question is, what is the established approach for the  
> calculations of
> electron affinity for the plane wave band dft calculations?

I believe, you should first ask (and answer) the preliminary  
question: what makes " ... the first conduction band ...  
meaningful ..?.. " The answer does not depend on the theoretical  
approach (DFT), nor on the basis set (plane waves), but on nature:  
the surface. So, in order to calculate electron affinities in an  
extended system you have to simulate "the place the added electron  
comes from", i.e. the vacuum, and the interface between that place  
and the solid, i.e. a surface.

Hope this clarifies a bit.

Stefano

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)

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