Kinetic Isotope Effects Continued: Variational Transition State Theory and Tunneling

2009 ◽  
pp. 181-202 ◽  
Author(s):  
Max Wolfsberg ◽  
W. Alexander Van Hook ◽  
Piotr Paneth
Keyword(s):  
Transition State ◽  
Transition State Theory ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Kinetic Isotope ◽  
Variational Transition State

A THEORETICAL STUDY FOR H2 + CN ↔ HCN + H REACTION AND ITS KINETIC ISOTOPE EFFECTS WITH VARIATIONAL TRANSITION STATE THEORY

2006 ◽  
Vol 05 (04) ◽  
pp. 769-777 ◽  
Author(s):  
LI-PING JU ◽  
KE-LI HAN ◽  
JOHN Z. H. ZHANG
Keyword(s):  
Transition State ◽  
Rate Constants ◽  
Transition State Theory ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
State Theory ◽  
Variational Transition State Theory ◽  
Kinetic Isotope ◽  
Theoretical Predictions ◽  
Variational Transition State

We present variational transition state theory (VTST) calculations for the H 2 + CN → HCN + H (R1) and D 2 + CN → DCN + D (R2) reactions and their reverses based on a global many-body expansion potential energy surface (PES) for ground-state H 2 CN (ter Horst MA, Schatz GC, Harding LB, J Chem Phys105:558, 1996). It is found that the tunneling effects are negligible over the 200–2000 K temperature range and non-negligible over 100–200 K for R1 and R2 reactions. The C–N bond acts almost as a spectator for both reactions. The present VTST rate constants are in good agreement with the available experimental results and the previous theoretical predictions for R1 and R2 reactions except for the overestimation of rate constants by VTST at lower temperatures that may be caused by recrossing effect. Additionally, the kinetic isotope effects are important for the forward R1 and R2 reactions, but not for the reverses of R1 and R2.

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