Intrinsic reaction coordinates optimization techniques

Techniques have been developed within the CASSCF method to characterize the critical points on the excited-state PES. Analytic first and second derivatives mean that minima and saddle points can be located using traditional energy optimization procedures. More importantly, intersections can also be located using constrained minimization [42,43]. Of particular interest for the mechanism of a reaction is the minimum energy path (MEP), defined as the line followed by a classical particle with zero kinetic energy [44-46]. Such paths can be calculated using intrinsic reaction coordinate (IRC) techniques... 

VAMP includes the standard Mclver-Kormonicki SADDLE technique for locating points close to transition states, but generally one- or two-dimensional reaction coordinate calculations are a better choice for locating starting points for transition state optimizations. There are two transition state optimizers available the transition state variation of EF and Powell s NS01A, which has proven to be extremely reliable in many applications. Intrinsic reaction coordinate (IRC) calculations allow the reaction path to be followed from the transition state to starting materials and products. VAMP has been used extensively for dynamics calculations on electron-transfer reactions and conductance in polymers. ... 

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