Hi Satty,

The crystal data in your inp file came from the paper. I checked the International
Crystal Structure Database (ICSD) - printout attached. The structure data in the paper
are not in standard form - atoms might not give the correct results if the input is bad- and there
are typos for two of the O5 coordinates according to the ICSD warning.
Does your institution have access to the ICSD - Online or on disc? If you
are not familiar with it, try talking to one of your institution's reference librarians.

I'm not certain what you mean by the corner-corner Mn. You were choosing Mn1
as the core in your inp. When I look at the structure, Mn1 sits in the middle of
the set of 3 octahedra that make up a side of the tunnel. Where would the corner-corner
distance be relative to the middle of the chain? You have 4 different Mn sites.

Fitting in R-space is common.

As for learning about crystal structures, try sitting in on a coordination chemistry
or solid state chemistry course. For a basic learning book, I like West's "Basic Solid
State Chemistry" or Muller's "Inorganic Structural Chemistry" (again, try the library
if you don't want to buy a copy). More recent books may be available. A bit of
googling may reveal some online lessons, like:
http://www.seas.upenn.edu/~chem101/sschem/solidstatechem.html

regards,
Robert

On 2/6/2014 3:16 AM, Sathish Mayanna wrote:

Hi

I am having some problem to get the real crystallographic parameters for Todorokite (I know there are many literature available) I used the parameters from Post et al 1988 (Rietveld refinement of the Todorokite structure) and others as well (attached Todorokite.inp file).

I except the corner corner Mn in Todorokite, since its a tunnel structure, but the Feff calculations do not provide any corner corner Mn, in addition I cannot fit exactly even Mn-O or Mn-Mn.

But If I use Ramsdellite (attached Ramsdellite.inp file), which is also a tunnel structure, I could get the Corner-Corner Mn and can fit perfectly the Mn-O, Mn-Mn, but cannot fit in K space.

It would be really great, if anyone could provide me the model Tunnel type-Mn oxide crystallographic parameters to fit the data (attached Mn Spectra.prj)

p.s: I tried my best to learn and understand the crystallographic parameters and miller indices, but still I feel that I am very poor, it would be nice, if someone suggest some good and basic source to learn more about pure mineralogy (which is crucial to know the basic parameters for fitting in Artemis).
--
Satty
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Dr. Robert Gordon
Staff Scientist, PNCSRF
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