A quantum mechanical insight into SN2 reactions: Semiclassical initial value representation calculations of vibrational features of the Cl${}^{-}$--CH${}_3$Cl pre-reaction complex with the VENUS suite of codes

Abstract

The role of vibrational excitation of reactants in driving reactions involving polyatomic species has been often studied by means of classical or quasi-classical trajectory simulations. We propose a different approach based on investigation of vibrational features of the Cl${}^{-}$--CH${}_3$Cl pre-reaction complex for the Cl${}^{-}$ + CH${}_3$Cl SN${}_2$ reaction. We present vibrational power spectra and frequency estimates for the title pre-reaction complex calculated at the level of classical, semiclassical, and second-order vibrational perturbation theory on a pre-existing analytical potential energy surface. The main goals of the paper are the study of anharmonic effects and understanding of vibrational couplings that permit energy transfer between the collisional kinetic energy and the internal vibrations of the reactants. We provide both classical and quantum pictures of intermode couplings and show that the SN2 mechanism is favored by the coupling of a C--Cl bend involving the Cl${}^{-}$ projectile with the CH${}_3$ rocking motion of the target molecule. We also illustrate how the routines needed for semiclassical vibrational spectroscopy simulations can be interfaced in a user-friendly way to pre-existing molecular dynamics software. In particular, we present an implementation of semiclassical spectroscopy into the VENUS suite of codes, thus providing a useful computational tool for users who are not experts of semiclassical dynamics.

References in corpus (11)

• First-Principles Semiclassical Initial Value Representation Molecular Dynamics
• Semiclassical "Divide-and-Conquer" Method for Spectroscopic Calculations of High Dimensional Molecular Systems
• On-the-fly ab initio semiclassical dynamics: Identifying degrees of freedom essential for emission spectra of oligothiophenes
• Ab initio Molecular Dynamics in Adaptive Coordinates
• 'Divide-and-conquer' semiclassical molecular dynamics: An application to water clusters
• The Importance of the Pre-exponential Factor in Semiclassical Molecular Dynamics
• "Divide and Conquer" Semiclassical Molecular Dynamics: A practical method for Spectroscopic calculations of High Dimensional Molecular Systems
• Mixed Semiclassical Initial Value Representation Time-Averaging Propagator for Spectroscopic Calculations
• Validating and Implementing Modified Filinov Phase Filtration in Semiclassical Dynamics
• Application of the Mixed Time-averaging Semiclassical Initial Value Representation method to Complex Molecular Spectra
• Graphics processing units accelerated semiclassical initial value representation molecular dynamics

Cited by in corpus (6)

• An Effective Semiclassical Approach to IR Spectroscopy
• Improved semiclassical dynamics through adiabatic switching trajectory sampling
• Reduced Rovibrational Coupling Cartesian Dynamics for Semiclassical Calculations: Application to the Spectrum of the Zundel Cation
• Vibrational Investigation of Nucleobases by Means of Divide and Conquer Semiclassical Dynamics
• Semiclassical vibrational spectroscopy with Hessian databases
• Representing Molecular Ground and Excited Vibrational Eigenstates with Nuclear Densities obtained from Semiclassical Initial Value Representation Molecular Dynamics