Linear constraints are implemented for the frame order models using the log-barrier constraint algorithm in minfx, as this does not require the derivation of gradients.
The pivot point and average domain position parameter constraints in Ångstrom are:
These translation parameter restrictions are simply to stop the optimisation in the case of model failures. Converting these to the A⋅x b matrix notation required for the optimisation constraint algorithm, the constraints become
For the order or motional amplitude parameters of the set , the constraints used are
These reflect the range of validity of these parameters. Converting to the A⋅x b notation, the constraints are
The pseudo-elliptic cone model constraint θx θy is used to simplify the optimisation space by eliminating symmetry.
The relax user manual (PDF), created 2020-08-26.