Determination of the intrinsic reaction coordinate: Comparison of gradient and local quadratic approximation methods

Abstract

The determination of the intrinsic reaction coordinate (IRC) by gradient methods often fails or is very inefficient when gradients vary markedly between coordinates as occurs in asymptotic regions of bimolecular surfaces. The alternative local quadratic approximation (LQA) approach, based on second derivatives of the surface, is shown to be generally accurate and efficient.