Virial theorem implications for the minimum energy reaction paths

Abstract

The virial theorem for the cut of the fixed-nuclei potential energy surface, along the minimum energy path (MEP) is discussed. The partitioning of such MEP profiles of the reaction potential barriers into kinetic ( T) and potential ( V) parts is qualitatively examined and the illustrative, quantitative examples of the virial theorem partitioning for the BEBO barrier profiles of the HH + H → H + HH, and the FH + H → F + HH, collinear exchange reactions are presented. The use of the MEP integral virial theorem as a criterion of the reliability of calculated shapes of potential barriers is suggested and variational definitions of the MEP in terms of the T and V surfaces, respectively, are given. The implications of the T and V smoothness condition at the saddle point, on the position of the barrier maximum between the initial and final states of chemical reactions are explored and illustrative applications to H-atom exchange reactions are presented.