Microcanonical variational theory with a semiclassical adiabatic ground-state transmission coefficient predicts the thermal rate constant for collinear H + Cl2 within 6% for 200-1000 K and the kinetic isotope effect kH/kD within 6 or 9% (depending on the detailed assumptions in the transmission coefficient) over the same temperature range. Other versions of variational transition-state theory and even conventional transition-state theory with semiclassical or quantum mechanical adiabatic ground-state transmission coefficients are also tested and show similar accuracy. The variational calculations predict a greater breakdown of conventional transition-state theory at higher temperatures and for three-dimensional reactions. The unified statistical theory is less accurate than variational transition-state theory for the magnitudes of the collinear rate constants, but more accurate for collinear kinetic isotope effects.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of physical chemistry|
|State||Published - Dec 1 1980|