A QUANTITATIVE APPROACH TO STRUCTURAL SIMILARITY FROM MOLECULAR TOPOLOGY OF REACTION PATHS

A general discussion is provided on the changes in shape of a continuum of molecular surfaces along a reaction path. The path is partitioned in terms of the shape characteristics of the nuclear configurations. The most important feature of this partitioning is the eventual occurrence of a region where more than one shape can be associated with the molecular surface continuum. This region is a formal boundary range between different molecular shapes. Position and width of this range, as well as other related parameters, are introduced as measures of structural similarity along a reaction path. Examples of simple triatomic reactions are considered in order to show the relation between these similarity descriptors and the change of energy content along the path.