[cctbxbb] fractional coordinate expansion ... share occupancy

[David A Carr]

Ralf,

I apologize for the unclear nature of my previous question.  As a protein scientist I am rather new to inorganic solids and am not certain how to deal with the site occupancy fractions ("sof"s) that accompany the coordinate entries in the ICSD data.  I was wondering if there is a method in cctbx for placement(selection) of the atoms that have fractional shared occupancy, as in the zeolite example that I posted.

To clarify in the example I posted the Al and Si atoms share the same reduced coordinates with sof's of .3 and .7 respectively.  In the unit cell that is returned by cctbx contains the overlapping points. 

My question is what is the best method for generating the correct distribution of atoms at these points.  Naively, one would just randomly select 30% of the shared points to be aluminums and set the other 70% as silicon.  I doubt that this is ideal.  


Thanks,

Andrew

 
***************************************
Dr. D. Andrew Carr
George Mason University
dcarr2 at gmu.edu


----- Original Message -----
From: "Ralf W. Grosse-Kunstleve" <rwgk at yahoo.com>
Date: Saturday, February 3, 2007 12:44 pm
Subject: Re: [cctbxbb] fractional coordinate expansion ... share occupancy

> Hi David,
> 
> > I have provided an example compound with scatterer code below as you
> > will note the output has overlapping atoms and the resulting 58 
> points> are not enough to cover the chemical formula. What do I 
> need to do to
> > fix this?
> 
> Sorry, I don't understand the question. Could you please explain
> what you expect to see as the output?
> 
> Ralf
> 
> 
> 
> 
> 
> 
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