The ABINIT Users Mailing List ( CLOSED )

[tgrassma@chem.ucsd.edu]

Well, the main problem is that DFT does not predict a band-gap for certain 
semiconductors, and there are only a few different methods that are said (or 
are expected to) fix this problem.  One of these solutions is the GW 
approximation.  Most people use in-house GWA code (such as Godby's) to 
accomplish this, but I'm not a programmer nor do I have access to such code.  
ABINIT is the only commercially available ab initio package that I've found 
to impliment GWA, but from what I've read in the manual it seems to be a 
relatively low-level implimentation.  It seems that the manual only really 
states that the GW code within ABINIT can be used for calculation of ionic 
states, but what I was wondering was if it was possible to use it on 
semiconductor surfaces (specifically, of those semiconductors which are known 
to be problematic for regular old LDA/GGA-DFT).  I realize that GW 
calculations tend to be rather difficult and are quite computationally 
expensive, so I wouldn't be surprised if the GW implimentation was inadequate 
(although I'd be quite happy if it was possible).

Another possibility is, however, to use TD-DFT.  I've heard some speculation 
that it, too, may give band-gaps for these problematic semiconductor 
materials.  However, as was mentioned in a previous thread, there is no real 
documentation for the TD-DFT portion of ABINIT.  So, I am also curious as to 
whether anyone knows whether or not this will work for my problems.  And if 
so, how do you actually use it?

Sorry for such a long post, but I do appreciate any advice or recommendations 
that come my way.  Thanks.

Tyler Grassman
Kummel Group
U. of CA, San Diego