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Converts span and skew representation of a 3x3 interaction tensor into the corresponding matrix.




Isotropic part, span, and skew are often seen in the literature. It is not a good way of reporting an interaction tensor (the original matrix is best), but it is still being used.


       iso  - isotropic part of the interaction, defined as
              (xx+yy+zz)/3 in terms of eigenvaues

        sp  - interaction span, defined as the difference 
              between the largest and the smallest eigenvalue

        sk  - interaction skew, defined as 3*(yy-iso)/sp
              where yy is the middle eigenvalue

       alp  - alpha Euler angle in radians

       bet  - beta Euler angle in radians

       gam  - gamma Euler angle in radians


    M  - 3x3 matrix


The reverse transformation (from matrix into span, skew, and angles) is ill-defined.

See also

eeqq2nqi.m, castep2nqi.m, euler2dcm.m, xyz2dd.m, axrh2mat.m

Version 2.1, authors: Ilya Kuprov