Define clusters of spins for joint optimisation.
cluster_id: The cluster identification string.
spin_id: The spin identifier string for the spin or group of spins to add to the cluster.
In a relaxation dispersion analysis, the parameters of the model of dispersion can either be optimised for each spin system separately or a number of spins can be grouped or clustered and the dispersion model parameters optimised for all spins in the cluster together. Clusters are identified by unique ID strings. Any spins not within a cluster will be optimised separately and individually.
If the cluster ID string already exists, the spins will be added to that pre-existing cluster. If no spin ID is given, then all spins will be added to the cluster.
The special cluster ID string `free spins' is reserved for the pool of non-clustered spins. This can be used to remove a spin system from an already existing cluster by specifying this cluster ID and the desired spin ID.
To add the spins `:1@N' and `:3@N' to a new cluster called `cluster', type one of:
[numbers=none] relax> relax_disp.cluster('cluster', ':1,3@N')
[numbers=none] relax> relax_disp.cluster(cluster_id='cluster', spin_id=':1,3@N')