The ABINIT Users Mailing List ( CLOSED )

[vincent.chevrier@dahn.phys.dal.ca]

Hi,
I'm studying the different phases in the Li-Si binary.
The phases have the following experimental band gaps:

Si      1.17 eV
Li12Si7 0.6 eV
Li7Si3  0.08 eV
Li13Si4 ?
Li22Si5 ?
Li      Metal

I am studying these phases with GGA pseudopotentials and I know I should 
expect calculated band gaps to be smaller and therefore Li7Si3, Li13Si4, 
Li22Si5 to likely have no gap.

I ran calculations on all the mixed phases with occopt 4 and tsmear 0.04, and 
the results were reasonably good but I didn't look into the question of band 
gaps at the time.

I have two main questions (with sub questions!):

1) For my research I need to compare the energies of the different phases and 
from Pierre-Matthieu Anglade's notes 
(http://anglade.googlepages.com/anglade-lecture-notes-on-abinit.pdf) I have 
learned that calculations with different tsmear cannot be compared. What 
about calculations with different occopt (1 and 4) be compared?
        1.1) If I can compare them are there any extra considerations for 
tsmear?

2) Do I choose occopt based on the experimental or calculated band gap?
        2.1) If I look for a band gap using calculated data, do I use occopt 
1 or occopt 4 for calculations?
        2.2) Is a DOS output (prtdos 1) enough or do I have to make a band 
structure diagram?
        2.3) If I have to consider individual bands, can I only look at high 
symmetry k-points? (from http://www.cryst.ehu.es/cryst/get_kvec.html)

Thanks for your help!

Vincent Chevrier
PhD Candidate
Physics Department
Dalhousie University