Dear Frank,
DIRAX is very good at finding the twin lattices in case of non-merohedral
twinning. In the reticular case you might want to use the LEPAGE-TWIN routine
in PLATON to find the correct subcell.
My collegue, Martin Lutz, suggests to change the measurement temperature in
order to chang
Matheus, Ian, Frank, Jonathan
Thanks for all the comments.
It is easy to calculate the amount of splitting of the spots once the
cell dimensions of each component are known. For the P212121 case, with
a-b twinning, splitting will be zero in the c* direction. The splitting
will increase as h and k
Dear Colleagues,
I hope the following detailed review will be of help both with terminology
as well as case studies of a wide variety of kinds, including possible
approaches for moving forward, regarding the various manifestations of
twinning, lattice disorders and multiple crystals.
Best wishes,
J
I recently ran into a similar case where the SG was P2(1)2(1)2(1) with a
~ b (within a few angstroms), thus emulating a P422 metric symmetry.
Full details here: Pubmed ID: 20057079
As Ian says, sometimes the spot splitting was particularly visible,
sometimes it was not. SAINT was not able to i
My experience with pseudo-merohedral twinning (it was actually the
reticular case with half the spots overlapped and the other
non-overlapped half on a pseudo C-centred lattice) is that the degree
of splitting varies widely over the diffraction pattern. In some
places there was complete overlap,
On Tue, Jun 22, 2010 at 11:09 PM, wrote:
> My interest was really what happened in the observed diffraction
> pattern. With the large difference in the orthorhombic cell dimensions,
> the spots will gradually separate for the higher orders. The point I
> really wanted to discuss was whether ther
comments appreciated.
Cheers
Colin
> -Original Message-
> From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On
> Behalf Of Ian Tickle
> Sent: 22 June 2010 17:35
> To: CCP4BB@JISCMAIL.AC.UK
> Subject: Re: [ccp4bb] Merohedral twining for P212121.
>
> On Tue,
On Tue, Jun 22, 2010 at 4:32 PM, Colin Nave wrote:
> Secondly, the difference in the cell dimensions (b=123.92 and c=128.89A)
> appears to be quite large and should lead to split spots which (I think)
> corresponds to non merohedral twinning. Did you observe these but integrated
> them as one?
Th
er more nor less" As important a philosopher as Wittgenstein.)
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of
Matheus Pinheiro
Sent: 22 June 2010 12:00
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] Meroh
Hi Yang,
I had the experience to work with twinning in P212121space group. My crystals
belong to space group P212121with unit cell dimensions a=82.39, b=123.92 and
c=128.89A. You can see that"b" and "c" are not equal but very simmilar, and
this factcan allow twinning for this space group. The c
Yang,
There are not any merohedral twin laws, but there are several
pseudomerohedral twinning possibilities. The most common would be a
monoclinic cell with a beta ~90, so it appears orthorhombic. Going the
other way, you could have an orthorhombic cell look tetragonal if A and
B are close
tion a = b, but the space group is P212121...)
Fred.
> Message du 21/06/10 22:52
> De : "yang li"
> A : CCP4BB@JISCMAIL.AC.UK
> Copie à :
> Objet : [ccp4bb] Merohedral twining for P212121.
>
> Dear all,
> Is there any possible of twining for a normal P2
Dear all,
Is there any possible of twining for a normal P212121 spacegroup and
what is the twin law, say no equal cell dimensions?
Some people said there is no twin law for such symmetry but I am not very
sure. Thanks a lot.
Best
Yang
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