Name
DISSOC — Define the dissociation threshold for CHN methods.
Description
When a system dissociates into fragments, some of its Hessian eigenvalues become zero.
When this happens the FULLCHN method
can no longer know the index of the Hessian (its number of strictly negative eigenvalues),
which may cause many wasteful cycles. A criterion based on the bond order matrix recognizes
the occurrence of fragments to prevent these useless cycles. A structure will be considered
dissociated if the bond order is less than the dissociation threshold. By default the
dissociation threshold is 0.05 and cannot be larger than 0.2. By prescribing DISSOC=0, FULLCHN
will scrutinize reorganization of the geometry within a single fragment.
