How to calculate Fermi Energy ?

[phoudha]

Hi,

I am writing you to ask you a question concerning the Fermi Energy.
If I make a calculaltion on platinum crystal, using Charge Density and Density of States option, I wanted to know where can I find the value of the Fermi Energy.
Because, the value I found in the file DensityofStates.data gave me a value around 0.537 . I found also 7.3eV in the DOS_OUTCAR.out file of VASP, so which one I have to choose.
Secondly, If I use a surface model, the Fermi Energy value should change doesn't it ?
Thanks for your attention.
Sincerely,
Phoudha

[admin]

1) for bulk systems with infinite periodic translation symmetry, the Fermi level is only defined to within a constant offset (please have a look to any solid state physics textbook).
2) for slabs, please use the LVTOT=True input tag, and vtotav.f to find the energy of the vacuum level. All energies can be taken with respect to that level.
3) the Fermi level as calculated for a slab differs from the bulk Fermi level in general.

[Modey3]

admin,

I'm assuming you mean that the Fermi Energy is defined to within a constant offset with respect to the vacuum level. If you know the experimental work functions of two materials, say Fe and Al, is it appropriate to set the zero-energy at the vacuum level of say the Fe-slab and offset the Al Fermi Energy from the Fe Fermi Energy by the difference in work functions.

Best Regards

modey3