Hello all,
I am trying to understand how the anisotropic displacement parameters
output by shelxl in the form U11 U22 U33 U23 U13 U12 relate with the
displacement in the x, y and z directions of say an ellipsoid in ORTEP.
So far I tried to find the eigenvalues for the matrix using the relationship
|Ucart - (lambda)I|=0
where lambda would give the eigenvalues along the three principal axis. In
the above relationship, I assumed the | | to stand for absolute value and
used just basic algebra to find the value of lambda, which will be the
inverse matrix for Ucart in this case. I used the reference
On the handling of atomic anisotropic displacement
parameters
R. W. Grosse-Kunstleve* and P. D. Adams
J. Appl. Cryst. (2002). 35, 477±480
to look up the above relationship. In the paper it is mentioned that
|Ucart - (lambda)I|=0
is solved using Cardan's formula.
So I probably oversimplified my solution and have it wrong.
Can anyone please help me on this? Is there a simple way of knowing the
displacement along a major axis on the ellipsoid itself in terms of
Angstrom?
Thank you.
Arti S. Pandey
Chemistry and Biochemistry
Montana State University
Bozeman,MT 59717
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