[gpaw-users] Probing the character of molecular orbitals

[Miguel Caro]

Hi all,

I am trying to use the scheme to project DOS onto molecular orbitals in
order to probe the sigma/pi character of an amorphous carbon network. I
have gone through the tutorial at

https://wiki.fysik.dtu.dk/gpaw/documentation/pdos/pdos.html#molecular-orbital-pdos

but still can't figure out how to do this properly.

At the moment I'm calculating the Kohn-Sham orbitals for an isolated
methane molecule whose C atom is centered at the same position as some C
atom in my amorphous network, and in a supercell of the same size. In
this way I make sure that the wave functions are commensurate (i.e. they
are given on the same grid). Methane has 4 sigma bonds, so I'm seeking
to probe the sigma character of my amorphous carbon KS states. To
achieve that, I calculate the PDOS from the overlap of the amorphous
carbon KS states and the methane KS states using the method outlined in
the online tutorial. The overlaps are nicely close to 1 in every case.
But obviously, the methane KS orbitals are nowhere near a complete basis
for my amorphous network, where I have of the order of 100s of atoms. So
basically I get a very poor description of the original DOS with this
approach.

I was thinking about constructing the KS basis set for the projection
from an array consisting of several copies of my methane orbitals
shifted in space so that they are centered at each and all of the C
atoms in the amorphous carbon network. But I'm not sure if this makes
much sense or if it's going to work at all.

I was wondering if someone has already tried to do something like this
before and how they went about it.

Many thanks,
Miguel
-- 
*Dr. Miguel Caro*
/Postdoctoral researcher/
Department of Electrical Engineering and Automation,
and COMP Centre of Excellence in Computational Nanoscience
Aalto University, Finland
Personal email: *mcaroba at gmail.com*
Work: *miguel.caro at aalto.fi*
Website: http://mcaroba.dyndns.org
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