Finding minimum energy reaction paths on ab initio potential energy surfaces using the fast marching method

The fast marching method (FMM) for determining minimum-cost paths has been extended to compute the minimum-energy reaction coordinates in chemical reactions. This was accomplished by building an interface between FMM and the Gaussian program. We demonstrate the new method using an SN2 reaction, the isomerization of HSCN to HNCS, and a gas-phase rearrangement reaction of relevance in mass spectrometry.