Publisher’s Note: “Path integral evaluation of equilibrium isotope effects” [J. Chem. Phys. 131, 024111 (2009)]

2009 ◽  
Vol 131 (4) ◽  
pp. 049903 ◽  
Author(s):  
Tomáš Zimmermann ◽  
Jiří Vaníček
Keyword(s):  
Path Integral ◽  
Isotope Effects ◽  
Chem Phys ◽  
Integral Evaluation

scholarly journals Path integral evaluation of equilibrium isotope effects

2009 ◽  
Vol 131 (2) ◽  
pp. 024111 ◽  
Author(s):  
Tomáš Zimmermann ◽  
Jiří Vaníček
Keyword(s):  
Path Integral ◽  
Isotope Effects ◽  
Integral Evaluation

Vapour Pressure Isotope Effect on Evaporation from Pure Organic Phases - a PIMD Approach

2020 ◽  
Author(s):  
Luis Vasquez ◽  
Agnieszka Dybala-Defratyka
Keyword(s):  
Path Integral ◽  
Vapour Pressure ◽  
Density Functional ◽  
Isotope Effects ◽  
Tight Binding ◽  
Decomposition Analysis ◽  
Energy Decomposition Analysis ◽  
Special Importance ◽  
Non Covalent Interactions ◽  
Covalent Interactions

<p></p><p>Very often in order to understand physical and chemical processes taking place among several phases fractionation of naturally abundant isotopes is monitored. Its measurement can be accompanied by theoretical determination to provide a more insightful interpretation of observed phenomena. Predictions are challenging due to the complexity of the effects involved in fractionation such as solvent effects and non-covalent interactions governing the behavior of the system which results in the necessity of using large models of those systems. This is sometimes a bottleneck and limits the theoretical description to only a few methods.<br> In this work vapour pressure isotope effects on evaporation from various organic solvents (ethanol, bromobenzene, dibromomethane, and trichloromethane) in the pure phase are estimated by combining force field or self-consistent charge density-functional tight-binding (SCC-DFTB) atomistic simulations with path integral principle. Furthermore, the recently developed Suzuki-Chin path integral is tested. In general, isotope effects are predicted qualitatively for most of the cases, however, the distinction between position-specific isotope effects observed for ethanol was only reproduced by SCC-DFTB, which indicates the importance of using non-harmonic bond approximations.<br> Energy decomposition analysis performed using the symmetry-adapted perturbation theory (SAPT) revealed sometimes quite substantial differences in interaction energy depending on whether the studied system was treated classically or quantum mechanically. Those observed differences might be the source of different magnitudes of isotope effects predicted using these two different levels of theory which is of special importance for the systems governed by non-covalent interactions.</p><br><p></p>

On the Path Integral Evaluation of the S-Matrix for Noncentral Potentials

2020 ◽  
pp. 187-198
Author(s):  
M. V. Carpio-bernido ◽  
E. B. Gravador ◽  
C. C. Bernido
Keyword(s):  
Path Integral ◽  
Integral Evaluation ◽  
S Matrix

Chapter 5. Kinetic Isotope Effects from Hybrid Classical and Quantum Path Integral Computations

2009 ◽  
pp. 105-131 ◽  
Author(s):  
Jiali Gao ◽  
Kin-Yiu Wong ◽  
Dan T. Major ◽  
Alessandro Cembran ◽  
Lingchun Song ◽  
...  
Keyword(s):  
Path Integral ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope

scholarly journals Femtosecond real-time probing of reactions. XIV. Rydberg states of methyl iodide

1994 ◽  
Vol 72 (3) ◽  
pp. 947-957 ◽  
Author(s):  
Hua Guo ◽  
Ahmed H. Zewail
Keyword(s):  
Methyl Iodide ◽  
Theoretical Calculations ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Rydberg States ◽  
Chem Phys ◽  
Two Dimensions ◽  
Special Focus ◽  
Methyl Radical ◽  
Valence States

The elementary reaction dynamics of methyl iodide in two Rydberg states leading to an iodine and a methyl radical occur on the femtosecond time scale (M.H. Janssen, M. Dantus, H. Guo, and A.H. Zewail. Chem. Phys. Lett. 214, 281 (1993)). In this article, we consider the dynamics of this elementary process which involves both the Rydberg and valence states. Direct comparisons are made between theory and experiment with special focus on the following observations: large isotope effects, mode dependence of the predissociation rates, and coherence effects. The quantal molecular dynamics in two-dimensions show that the initial wave packet motion occurs along a vibrational mode involving the light atoms accompanied by transitions from the Rydberg state to the repulsive state; subsequent dynamics on the dissociative state lead to the C—I bond cleavage. The theoretical calculations also give the decay behavior of the Rydberg states with lifetimes in agreement with those observed in the femtosecond experiments. Moreover, the large isotope effect in observed predissociation rates of CH3I and CD3I has been successfully reproduced by the same model. The two-dimensional dynamics underscore the shortcomings of a one-dimensional picture in which the C—I serves as the sole reaction coordinate. The model presented here offers a viable mechanism for the dynamics of these Rydberg states.

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