Canonical variational theory

Several VTST techniques exist. Canonical variational theory (CVT), improved canonical variational theory (ICVT), and microcanonical variational theory (pVT) are the most frequently used. The microcanonical theory tends to be the most accurate, and canonical theory the least accurate. All these techniques tend to lose accuracy at higher temperatures. At higher temperatures, excited states, which are more difficult to compute accurately, play an increasingly important role, as do trajectories far from the transition structure. For very small molecules, errors at room temperature are often less than 10%. At high temperatures, computed reaction rates could be in error by an order of magnitude. 

CVT (canonical variational theory) a variational transition state theory technique... 

A.D. Isaacson, D.G. Truhlar, Polyatomic canonical variational theory for chemical reaction rates. Separable-mode formalism with application to OH+I-p H2O+H, J. Chem. Phys. 76 (1982) 1380. 

The Canonical Variational Theory [39] is an extension of the Transition State Theory (TST) [40,41]. This theory minimizes the errors due to recrossing trajectories [42-44] by moving the dividing surface along the minimum energy path (MEP) so as to minimize the rate. The reaction coordinate (s) is defined as the distance... 

Canonical variational theory (CVT) is obtained by minimizing the generalized transition state rate expression s) with respect to the location s of the divid-... 

Figure 27.6 Rate constants as a function of temperature forthe collinear Cl + HBr reaction. Accurate quantum mechanical rate constants (solid line with bullets) are compared with those computed using improved canonical variational theory (ICVT) with tunneling included by SCSAG (dotted line) and LCG3 and LAG (long dashed line).

Alhambra C, Corchado J, Sanchez M, Garcia-Viloca M, Gao J, Truhlar DG. Canonical variational theory for enzyme kinetics with the protein mean force and multidimensional quantum mechanical tunneling dynamics. Theory and application to liver alcohol dehydrogenase. J Phys Chem B 2001 105 11326-11340. 

A. D. Isaacson and D. G. Truhlar, /. Chem. Phys., 76, 1380 (1982). Polyatomic Canonical Variational Theory for Chemical Reaction Rates. Separable-Mode Formalism with Application to OH + H2 -> H2O + H. 

We briefly summarize the Truhlar-Garrett canonical variational theory (CVT) Which represents a definite realization of an old proposal for constructing free-energy surfaces (cf. for instance Ref.llba). It may be characterized by three steps... 

Canonical variational theory finds the best dividing surface for a canonical ensemble, characterized by temperature T, to minimize the calculated canonical rate constant. Alternative variational transition state theories can also be... 

Phys. Chem. B, 105, 11326 (2001). Canonical Variational Theory for Enzyme Kinetics with the Protein Mean Force and Multidimensional Quantum Mechanical Tunneling Dynamics. Theory and Application to Liver Alcohol Dehydrogenase. 

B. C. Garrett and D. G. Truhlar, Improved canonical variational theory for chemical reaction rates. Classical mechanical theory and applications to collinear reactions, J. Phys. Chem. 84 805 (1980). 

---