For the free rotor variation of the isotropic cone model, the torsion angle restriction is absent and the model parameters are

where *P*_{i} are the average domain position translations and rotations, *E*_{i} are the spherical angles defining the cone axis, *p*_{i} are the coordinates of the pivot point, and
*θ*_{max} is the maximum cone opening half-angle.

The relax user manual (PDF), created 2016-10-28.