Test of Variational Transition State Theory against Accurate Quantal Results for a Reaction with Very Large Reaction-Path Curvature and a Low Barrier

摘要

We present three sets of calculations for the thermal rate constants of the collinear reaction I+HI yield IH+I; accurate quantum mechanics, conventional transition state theory (TST), and variational transition state theory (VTST). This reaction differs from previous test scores in that it results by factors of 20 billion, 20,000, 57, and 19 at 40, 100, 300, and 1000 K respectivley. At these same four temperatures the ratios of the VTST results to be accurate quantal ones are 0.3, 0.8, 1.1, and 1.4, respectively. We conclude that the variational transition states are meaningful, even though they are computed from a reaction-path Hamiltonian with large curvature, which is the most questionable case.