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thanks a lot for all the reply concerning my question on dm-averaging.
Due to the proposals in the last week here is a short summary:
> Within the the asymmetric unit of my crystal there are six copies of the
> protomer grouped as three dimers A (consisting of A1 and A2), B and C.
> I could determine the following symmetry operators:
> inter-dimer: A -> B
> B -> C
> intra-dimer: A1 -> A2 (from subunit 1 of dimer A to subunit 2 of dimer 1)
> B1 -> B2
> C1 -> C2
> All symmetry operators are 2-folds with a transition-component. None of
> them falls on a crystallographic axis.
SORRY FOR THIS CONFUSING STATEMENT. I MENT THAT THE OPERATOR CONSISTS OF
THE 3X3 MATRIX AND A VECTOR.
> For the symmetry operations A -> B, A -> B and A1 -> A2 I use A as mask,
> for B1 -> B2 i use B as mask and for C1 -> C2 C as mask.
> The question:
> Are these symmetry operations enough to cover the whole symmetry?
> Or do I have to specify the operations A -> C, A1 -> B1, A1 -> B2 ,...
REPRESENTATIVELY FOR ALL THE ANSWERS THE SUGGESTION FROM KEWIN COWTAN:
> The following fundamental principle should be applied...
> YOU ONLY NEED ONE MASK FOR `dm'. IF YOU HAVE MORE THAN ONE MASK YOU
> ARE DOING SOMETHING WRONG (unless you are an expert and are solving a
> very specific problem, in which case you know all about it).
> What you need to do is supply one mask, which covers A1, and the
> operators which map A1-A1(*), A1-A2, A1-B1, A1-B2, A1-C1, A1-C2.
> If your dimer rotations are self-inverse, then you mask could equally
> well cover A instead of A1.
> If all 6 ncs ops form a closed group, then you could use a haxamer mask.
> (*)-the identity.
HOW TO GENERATE THE SYMMETRY OPERATOR FROM A1-B2 IF YOU JUST KNOW THE
OPERATORS A-B AND B1-B2?
(A1-B2) = (B1-B2)x(A-B): multiply the matrices, take the right order!
As all symmetry operators X consist of a 3x3 matrix M AND a vector t for
the multiplication you have to multiply the augmented 4x4 matrices:
(m11 m12 m13 t1)
X= M + t => (m21 m22 m23 t2)
(m31 m32 m33 t3)
( 0 0 0 1)
Take maple or a lot of paper to calculate the multiplication.
nicely smoothed averaged and phase extended maps!!!!!!!!
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