[Ifeffit] D-Atoms program, common positions and occupancies

Robert Gordon ragordon at alumni.sfu.ca
Mon Apr 7 18:29:06 CDT 2014

Hi Moneed,

Bruce is a busy fellow. I doubt he has time to double-check every user's 
input file.

Let's go through some steps that might help you.

What reference are you using for CdSe crystal structure?
What are (is) the Se positions (position) supposed to be in that structure
with the P63mc symmetry?... the Cd positions (position)?
What are they in your input file?

Only one unique atom should be specified for a given symmetry position 
that has
more than one symmetry-related atom in the unit cell.

More generally, how much do you understand about crystal structures and
symmetry? If the answer is "not much", taking a course on such would be 
or even reading about it in some standard inorganic or solid state 
chemistry texts.


On 4/5/2014 4:54 AM, Moneeb Shatnawi wrote:
> Dear Bruce Ravel,
> Hello,
>  I am Moneeb Shatnawi from the University of Jordan. I have a question 
> and I appreciate your help in advance.
>  I have installed the Demeter program (version 0.9.18) and I tried to 
> use your (D)Atoms program using the attached input files.
> When I try to run atoms, I get a warning message stating that two 
> sites generate one or more common positions and their occupancies sum 
> to more than 1. (attached also the warning message that I got).
> If I ignore this warning message and try to run FEFF, the program crashes.
> When I change the space group to P 1 (as indicated by the message) , 
> the program runs well.
> My question is, could you please figure out the problem with these 
> input files, so that I can run them with the correct space group?
> Thank you so much in advance,
>  Moneeb
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Dr. Robert Gordon
Staff Scientist, PNCSRF
APS Sector 20
9700 S. Cass Ave. 435E
Argonne, IL, USA 60439
630-252-0581 ph
630-252-0580 fax

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