I have constructed an exact model of the interaction matrix based on T.D. Smith, J. R. Pilbrow, Coord. Chem. Rev., 1974, 13, 173-278, eqn 14 (http://www.sciencedirect.com/science/ar ... 4500802556), and whose code I mention in viewtopic.php?f=3&t=474.

While it gives a very good agreement for angles xi = eta = 0 (collinear g-tensors) with

`Exp.Ordering = +1`

and without strains, as soon as I give a non-zero value to xi, the g|| component loses most of its intensity and the `Exp.Ordering = +1`

parameter is more or less neglected. The agreement breaks down even for infinitesimal xi angles.My question is whether my approach of constructing an explicit interaction Hamiltonian combined with

`Exp.Ordering = +1`

and/or hyperfines is valid for xi =/= 0. Is there some aspect of the problem's symmetry I overlooked?Thanks!