[Ifeffit] Ru input file - a question and a problem

[Bruce Ravel]

On Wednesday 02 May 2007, Vivek Murthi wrote:
> The problem:_
> 1. I got the crystallographic data for Ru from
> "database.iem.ac.ru/*mincryst*/" which I used inside atoms to generate
> FEFF a input file. However, FEFF returns an error saying that my atoms
> list might be wrong and that two atoms are separated by less than an
> 0.93 angstroms. I also checked the 5 digit precision in the input file
> to make sure that  wasn't creating the problem. The FEFF input file
> generated by atoms definitely has atoms bizarrely close to each other.  
> I do not understand why a standard crystallographic data would give such
> results. I have attached the "Ru.inp" input file I used and the error
> buffer from FEFF below for your convenience.

  <snip>


> ! This atoms input file was generated by Artemis 0.8.007
> ! Atoms written by and copyright (c) Bruce Ravel, 1998-2001
> title = ...
> space = P63/MMC
> a =       2.7040        b =       2.7040        c =       4.2820
> alpha =  90.0   beta =   90.0   gamma = 120.0
> core =  Ru      edge =  K       rmax =    3.0
> shift   0.00000   0.00000   0.00000
> atoms
> ! elem   x          y          z     tag           occ.
>   Ru    0.33330    0.66670    0.25000  Ru            1.00000



Vivek,

I suppose that I have used confusing language in the past.  In this
context, "five digits" means "five digits to the right of the decimal
place."

One way of avoiding this problem in Artemis is to use simple
fractions.  Instead of "0.33333", you can just enter "1/3".

B

P.S. The next version of Artemis checks for numbers that are close to
1/3 and 2/3 and prompts you to choose between the number you entered
and the fraction.  It's a bit annoying to have to answer a bunch of
dialog boxes, but it should help avoid this problem.



-- 
 Bruce Ravel  ---------------------------------------------- bravel at anl.gov

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