[Pw_forum] How to plot molecular hybrid orbitals for surface slab geometry?

[Axel Kohlmeyer]

On Sun, 2009-04-05 at 19:06 +0800, vega lew wrote:
> Dear all,
> 
> I'm studying the water splitting behavior on certain surfaces. And I
> have identified a special structural features of the surface for water
> dissociation.
> But I can't tell why that kind of feature did a positive effect on
> water dissociation. One visitor to our group thought this behavior has
> a strong dependence of molecular hybrid orbitals of atoms near the

was this person by any chance an organic chemist??

>  surface. From a Structural Chemistry viewpoint, certain atomic
> structure could result in different hybrid styles of molecular
> orbitals. The feature I identified may have a favorable shape of
> hybrid orbitals for water approaching and dissociating.

<climbing on soapbox>

you have to forget about the nice orbital pictures that you see in
chemistry text books. they are a visual crutch to break a problem
where everything interacts with everything into individual additive
components. it still works surprisingly well, but only after the fact,
i.e. you can rationalize findings that you got elsewhere in a simplified
form. 

</descending from soapbox>

> 
> I wonder whether QE has a function for ploting the shape of hybrid
> molecular orbitals near the surface.

this is what the gods of quantum chemistry created the population 
analysis for. after you project on atomic (pseudo) wavefunctions you
can determine the amount of s-,p-,d-character of your individual states.
this is not without problems, though. the partitioning is somewhat
arbitrary and the projection from plane waves to atomic orbitals is
not complete, i.e. you are missing out on some contributions that do
not fit into the atomic orbital basis you provide.

cheers,
   axel.

> 
> thank you for reading
> 
> best,
> 
> vega
> 
> -- 
> ==================================================================================
> Vega Lew ( weijia liu)
> PH.D Candidate in Chemical Engineering
> State Key Laboratory of Materials-oriented Chemical Engineering
> College of Chemistry and Chemical Engineering
> Nanjing University of Technology, 210009, Nanjing, Jiangsu, China
> ******************************************************************************************************************
> Email: vegalew at gmail.com
> Office: Room A705, Technical Innovation Building, Xinmofan Road 5#,
> Nanjing, Jiangsu, China  
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-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
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If you make something idiot-proof, the universe creates a better idiot.