[sdpd] A comment on indexing

[K.Shankland...@rl.ac.uk]

Lachlan said

>If the main(?) problem people encounter with solving from
>powders is reliable powder indexing - what percentage will
>ever get through to trying solve using programs such as DASH.
>(the above Round Robin was on a phase where the cell was given -
>as it was a "solving" round robin - not an indexing round robin)

I agree with Armel - who says that indexing is the big problem ? 
Lets keep things in perspective !  Structure solution is far 
from a "done deal". Yes, global optimisation and enhanced 
direct methods have transformed what might be considered to be 
tractable by powder diffraction, but there is still plenty 
of work to be done at this stage. 

Of the many compounds that we have solved over recent years, 
the vast majority of them have indexed first time, albeit
with mostly synchrotron data.  I suspect that there are just
as many indexed patterns that have not been solved yet as there
are unindexed patterns.

However, what is certainly true to say is that the ability 
to tackle and solve much larger structures invevitably leads 
us into an area where the unit cells are much larger and
existing methods are perhaps not so effective.  So it
seems likely that increased failure rates in indexing will
be a consequence of the success of global optimisation 
(and other) methods in structure solution.

Best,

Kenneth