Thanks Ian,
I understood now.
Great lesson for me.
Best regards
Fulvio Saccoccia
Il giorno ven, 20/05/2011 alle 18.14 +0100, Ian Tickle ha scritto:
The true values of the components of the twin can't in general be
equal since they come from _different_ reflections that are unrelated
by
Thanks Ian,
I tried to do this:
I took the file containing
hkl I and sigI
and generated a new file containing
hkl I/2 and sigI
because I know, from the refined structure that the twin fraction is
nearly 0.5. Now, using this new file the wilson plot give me a more
reliable estimated B
No, simply applying a single overall scale factor to the intensities
can't possibly make any difference to the Wilson B since the fall-off
with resolution will remain unchanged. The Wilson plot is a plot of
ln(mean(I')/S) in shells of constant d* vs d*^2, where I' is I
corrected for symmetry and
Thanks Ian,
but your reply confused me a little.
I hope you can explain me where I was wrong.
I know that
I(twin)=tf*I(h1)+(1-tf)*I(h2)
I supposed that having tf=0.5 I could take the I(twin), dividing by 2 I
will get both I(h1) and I(h2), that are the two component (that are
equal in
The true values of the components of the twin can't in general be
equal since they come from _different_ reflections that are unrelated
by the true crystal symmetry (they are only related by the
pseudo-symmetry of the twin).
Let's say:
Itwin(h1)=tf*I(h1)+(1-tf)*I(h2)
where I(h1) and I(h2) are
Hi Fulvio
There are 2 different issues here: the Wilson plot scale B factor on
the one hand and Wilson statistics on the other. The first are not
affected by twinning since they depend only on the intensity averages
in shells. The second refers to the distribution of intensities (i.e.
the
Ok, so another question in my mind:
the data come from a collection interrupted after the first 200 frames
and restarted after 1 hour to recover the missed 160 frames.
The first and second group of frames, if separately indexed, give cell
parameter values that differ of about 1A for axes and 1
Hi Fulvio,
Yes, it can. An increase in cell parameters can indicate a failure of the
cooling system or (more likely) radiation damage of the crystal.
For refinement you probably do not need all those 360 frames,
unless you collected thin frames and your space group is P1
I suggest you integrate
