A frontier mode-following method for mapping saddle points of conformational interconversion in flexible molecules starting from the energy minimum

A new transition-state search method for flexible molecules, frontier mode-following (FMF), which is a modification of the eigenvector-following method is developed. FMF is characterized by starting from an arbitrarily chosen energy minimum and climbing up a potential energy surface (PES), following more than one eigenvector. Both single-mode (only one vibrational mode is selected as a frontier mode) and dual-mode followings (two neighboring modes as frontier modes) were tested for locating the saddle points of n-pentane and cyclohexane on the MM2 PES. A combination of FMF and full-matrix Newton–Raphson methods was also applied to C6–C10 cycloalkanes for finding the unique minima and saddle points.