Keyword category:

Transition State Location: CHN Methods

DISSOC=n.n

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.