 The quadratic synchronous transit (QST) method extends LST by allowing a parabolic reaction path, with optimization of the highest energy point orthogonally to the parabola.In Nudged elastic band method, the beads along the reaction pathway have simulated spring forces in addition to the chemical forces, , to cause the optimizer to maintain the spacing constraint.Specifically, the force on each point "i" is given by

formula_4

where

formula_5

is the spring force parallel to the pathway at each point ("k" is a spring constant and , as before, is a unit vector representing the reaction path tangent at ).