PS: There's also a very nice book edited by Peter Mueller with guided tutorials
and example data (ranging from the simple to more complex cases), if you'd like
to check it out at some point:
Crystal Structure Refinement - A Crystallographer's Guide to SHELXL by Peter
Müller, Regine
Dear David,
I dare claim that rather you do not know how to use the listed programs
in the case for small molecule data rather than none of them were
optimised. E.g. 10degree frames loose all the possible accuracy in the
phi-direction so I am not surprised you had trouble indexing. There is
no
Dear Tim,
I am sure your statement is too general and is not very precise.
10 deg oscillation range is as precise as 0.1 deg. Positions of diffraction
spots on the area detector have
defined position on rotation axis within the precision/accuracy of the stepping
motor and the spacial
Dear Felix,
as far as I understand we are talking about the frame width, not the
total data range for indexing (10 degree rotations to get enough spots
per frame). I have used 180degrees of data for indexing. At least XDS
places the reflection at the centre of the frame so that with a 10deg
frame
Dear Tim,
My most experience is with HKL2000 which during the index doing something quite
mysterious and not very well described
such as a brute search for the correct reciprocal lattice. I do not know where
initially the reflections are placed by HKL2000,
but finally it converges. In the moment
Indexing involves storing all the reflection positions in orthogonal
reciprocal space and then finding a reciprocal lattice that fits most of
them.
For a 10 degree frame all we know is that a reflection lies somewhere on
a sort of 10 degree arc; only two of the three coordinates are
precisely
There are detectors that are small and have fast readout time and others
that have much larger size and slower readout time. Large detector size
reduces background level very effectively by allowing data collection with
larger crystal-to-detector distance. For well ordered crystals, level of
Hi Andreas -
My two cents, from having tried this a couple of times on small molecule
crystals that crossed my path:
- You can get an answer using only standard macromolecular
crystallography programs. It may not be up to the standards of the
small molecule community, but that's probably
Andreas,
What is your setup? We have a Cu Anode with an R-Axis IV, and just due
to the geometry, the maximum resolution we can collect is around 1.4A.
That won't do for small molecules. I think if your resolution is worse
than something like 0.85A alarm bells start going off.
If you can
Dear Andreas,
It's a closely guarded secret that the data collection for small molecules is
not that different from that for macromolecular crystallography. (Otherwise
there's the risk that more macromolecular folks might get hooked to the
addictive charm of the small-molecule world!)
Just
Dear Andreas,
if you find a single crystal, you can use your favourite program for
data collection, none of them should have problems with small molecule
data. Since data integration only takes the Laue group into account, the
space group make no problems, since also the Laue group of a protein
Coincidentally, I just spent my day trying to index a lattice of ~ 10 x
10 x 11 A.
Mounting samples: if the compound is stable, just glue it to the end of
a steel pin. No muss, no fuss.
We had to attenuate our synchrotron beam heavily to make it work; motors
can only turn so fast.
We did
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