[Pw_forum] Work function calculation of CNT

[Tuo-Hung Hou]

Hi!,

 

I am doing the work function calculation on carbon nanotubes. If I am not
mistaken, the scf calculation should give me Fermi energy or midgap between
HOMO and LUMO. Then, one can use pp.x plot_num 1 to generate the total
potential profile. The work function is decided by the difference between
the Fermi energy and the potential energy at the vaccum of the supercell. 

 

However, I am running into a problem that the Fermi energy from scf (1.65
ev) is higher than any potential inside the entire supercell (ranging from
-10.4 to 0.4 eV).  When I looked at both the charge and potential profiles,
they seemed to suggest the Fermi energy should be somewhere around -4 eV,
which is not even close to the value scf reported. I am very confused now.
What is the Fermi energy I can use? Any thoughts on this? 

 

Thanks

Tuo-Hung

_______________________________________

Tuo-Hung Hou

Cornell University

School of Electrical and Computer Engineering

325 Phillips Hall

Ithaca, NY 14853

phone: 607.255.4181

email : th273 at cornell.edu

 

 

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