Reaction coordinate

Plain simulations fail to capture so called rare events, because they are not feasible to occur in realistic computation times.

Many collective variables than span the reaction coordinate with a continuous function ξ: An example is the complexation of two molecules.

Special collective variables that help to distinguish reactants from products are also known as order parameters, terminology that originates in work on phase transitions.

[3] Reaction coordinates are special order parameters that describe the entire pathway from reactants through transition states and on to products.

It is typically chosen to follow the path defined by potential energy gradient – shallowest ascent/steepest descent – from reactants to products.

Diagram of a catalytic reaction, showing the energy level as a function of the reaction coordinate. For a catalyzed reaction, the activation energy is lower.