[TCOD] What structures do we accept to TCOD?

[Saulius Gražulis]

On 2014-07-28 11:23, Armel le Bail wrote:
> Since it is time to questions, I have one.
>
> DFT-optimized structures are done in a great variety of cases, one being
> when the refinement quality against experimental data (powder, etc) is
> poor due to an unfavourable ratio P/D (parameters/Data).
>
> However, I have almost never seen the comparison of the experimental
> data to the intensities calculated from the optimized atomic
> coordinates... I have especially in mind a "simple" example, calcium
> carbonate, vaterite form, for which dozens of optimized models were
> proposed, without even one comparison to the data...
>
> So the question is :
> In case of the existence of an experimental dataset, should a comparison
> observed/calculated be requested (classical R values but with fixed
> coordinates) ?

I thing that COD/TCOD comparison of the same crystal structure refined 
against Fobs and optimised with the advanced DFT methods would give an 
good overview of the correspondence, and that's what I would be very 
interested in.

I regard this as a win-win-win situation:

a) if both X-ray and DFT agree, we will have greater reassurance that 
both are correct (within experimental and computational errors);

b) if the disagree, then either:

b') the x-ray structure has problems

or

b'') the DFT computation has problems.

In both cases we can check the data, trace down the problems and 
(ideally) fix them.

I am currently in Cambridge with Peter Murray-Rust, and we had very 
interesting conversations with people who actually do similar things, 
for their own research. The results are very intriguing :). If we could 
get these people on board we could have valuable contributions, I hope.

Regards,
Saulius

-- 
Saulius Gražulis

Biotechnologijos institutas
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