Optimized multidimensional tunneling

Allison TC, Trahlar DG (1998) Testing the accuracy of practical semiclassical methods variational transition state theory with optimized multidimensional tunnelling. In Thompson DL (ed) Modern Methods for Multidimensional Dynamics Computations in Chemistry. World Scientific, Singapore, p 618... 

Table 6.2 Tests of Variational Transition State Theory by Comparing with Exact Quantum Calculations (Extracted from Allison, T. C. and Truhlar, D. G. Testing the accuracy of practical semiclassical methods variational transition state theory with optimized multidimensional tunneling, in Thompson, D. L., Ed. Modem methods for multidimensional dynamics computations in chemistry, World Scientific, Singapore 1998. pp 618-712. This reference quotes results on many more reactions and BO surfaces over broad temperature ranges.)The numbers in the table are ratios of the results of the approximate calculation to the quantum calculation, all at 300 K...

TST = conventional Transition State Theory, ICVT = Improved Canonical Variational Transition state theory, ICVT/SCT = ICVT/Small Curvature Tunneling, ICVT/p,OMT = ICVT/Microcanonical Optimized Multidimensional Tunneling. 

In ESP theory [30-32] we treat the system by the same methods that we would use in the gas phase except that in the nontunneling part of the calculation we replace V(R) by TT(R), and in the tunneling part we approximate V(R) by TT(R) or a function of TT(R). Next we review what that entails. In particular we will review the application of variational transition state theory [21-25] with optimized multidimensional tunneling [33,34] to liquid-phase reactions for the case [31,32] in which TT(R) is calculated from V(R) by... 

T. V. Albu, J. C. Corchado, D. G. Truhlar, J. Phys. Chem. A 105, 8465 (2001). Molecular Mechanics for Chemical Reactions A Standard Strategy for Using Multiconfiguration Molecular Mechanics for Variational Transition State Theory with Optimized Multidimensional Tunneling. 

The last three columns of Table 19.5 report results obtained with the micro-canonically optimized multidimensional tunneling approximation, which represents the currently most trusted method for including a tunneling contribution. These results predict that the hydrogen kinetic isotope effect for the hydrogen atom step in methylmalonyl-CoA reaction in the direction of succinyl formation is -100. 

T. D. (2004) Ensemble-averaged variational transition state theory with optimized multidimensional tunneling for enzyme kinetics and other condensed-phase reactions,... 

Mechanics for Chemical Reactions A Standard Strategy for Using Multiconfiguration Molecular Mechanics for Variational Transition State Theory with Optimized Multidimensional Tunneling. 

Tmhlar DG, Gao JL, Garcia-Viloca M, Alhambra C, Corchado J, Sanchez ML, Poulsen TD (2004) Ensemble-averaged variational transition state theory with optimized multidimensional tunneling for enzyme kinetics and other condensed-phase reactions, hit J Quantum Chem 100(6) 1136-1152... 

Albu TV, Corchado JC, Truhlar DG (2001) Molecular mechanics for chemical reactions a standard strategy for using multiconfiguration molecular mechanics for variational transition state theory with optimized multidimensional tunneling. J Phys Chem A 105 8465-8487... 

At this point one can include optimized multidimensional tunneling in each (i = 1,2,..., 7) of the VTST calculations. The tunneling transmission coefficient of stage 2 for ensemble member i is called and is evaluated by treating the primary zone in the ground-state approximation (see the section titled Quantum Effects on Reaction Coordinate Motion ) and the secondary zone in the zero-order canonical mean shape approximation explained in the section titled Reactions in Liquids , to give an improved transmission coefficient that includes tunneling ... 

Computations in Chemistry, D. L. Thompson, Ed., World Scientific, Singapore, 1998, pp. 618-712. Testing the Accuracy of Practical Semiclassical Methods Variational Transition State Theory With Optimized Multidimensional Tunneling. 

---