The Euler angle α must be supplied, if the coupling is not axially symmetric (η₀ ≠ 0). It corresponds to the angle by which the tensor has to be rotated around z^(PAS) so that y^(PAS) points along the node line, or, what is equivalent, until x^(PAS) lies in a common plane with both z^(PAS) and z^(CF). It is assumed that α is identical for each site.

Weblab uses euler angles according to the convention of Rose. For a description see here