The output cluster contains all properties of the initial atoms object, and some additional columns, which are: "index" : index of the cluster atoms into the initial atoms object. "termindex": nonzero for termination atoms, and is an index into the cluster atoms specifiying which atom is being terminated, it is used in collecting the forces. "rescale" : a real number which for nontermination atoms is 1.0, for termination atoms records the scaling applied to termination bond lengths "shift" : the shift of each atom