[Wien] How to subtract a particular orbital character from a valence electronic density?

[Elias Assmann]

On 07/21/2014 03:40 PM, Martin Gmitra wrote:
> I would like to plot valence density (lapw5) in a narrow energy window
> around Fermi level (calculated by lapw2 -all flag) to which I would
> like to subtract specific atomic orbital character. Say that the
> density can be expressed as a combination (due to hybridization) of
> atomic orbitals rho(r)=A(r) s + B(r) p + C(r) d + ..., where the
> coefficients A(r), B(r), C(r), ... reflect hybridization. My case
> would be to subtract, say d-orbitals as rho(r) - C(r) d. This differs
> from modifying case.inst (lstart -sigma flag) and subtracting
> case.sigma.
>
> It looks like to dig in QTL files or can you provide another solution
> or hint how to start?

If the bands in question are fully occupied, you could use Wannier 
functions.  Transform “all” bands to s,p,d-like WFs in one Wannier 
projection (using wien2wannier 
<http://www.ifp.tuwien.ac.at/forschung/arbeitsgruppen/cms/software-download/wien2wannier/> 
and Wannier90 <http://www.wannier.org/>), then either compute the 
density |w(r)|² of the d-like WFs using ‘wplot’ and subtract from the 
total density computed by lapw5; or add the densities of the other WFs 
from ‘wplot’.

Some points to keep in mind if you decide to try this:

* The wave functions output by wplot are currently not normalized to 
unity.  If you mix densities from lapw5 and wplot, you need to control 
this carefully.

* The WFs are not atomic orbitals, i.e. you will not get exactly what 
you describe (depending on what you want to do, I suppose this might be 
an advantage or a disadvantage).  Qualitatively, the more bands you 
include in your projection, the more they will approach the atomic 
orbitals.  See <http://arxiv.org/abs/1405.3804> or 
<http://arxiv.org/abs/1405.7232> for discussions of this with respect to 
specific materials.  This means you should think carefully about what 
kind of projection is appropriate.

* While anything you do with QTLs or similar will be limited to the MT 
spheres, the WFs are not affected by RMTs.  Of course, for very 
localized states this will make little difference.


	Elias


-- 
Elias Assmann
Institute of Solid State Physics
Vienna University of Technology
<http://www.ifp.tuwien.ac.at/cms/>