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
