Vibrational energy relaxation classical calculation

Equation (13.39) implies that in the bilinear coupling, the vibrational energy relaxation rate for a quantum hannonic oscillator in a quantum harmonic bath is the same as that obtained from a fully classical calculation ( a classical harmonic oscillator in a classical harmonic bath ). In contrast, the semiclassical approximation (13.27) gives an error that diverges in the limit T 0. Again, this result is specific to the bilinear coupling model and fails in models where the rate is dominated by the nonlinear part of the impurity-host interaction. 

J. L. Skinner and K. Park,/. Phys. Chem. B, 105,6716 (2001). Calculating Vibrational Energy Relaxation Rates from Classical Molecular Dynamics Simulations Quantum Correction Factors for Processes Involving Vibration-Vibration Energy Transfer. 

Skinner, ).L. and Park, K. (2001) Calculating vibrational energy relaxation rates from classical molecular dynamics simulations quantum correction factors for processes involving vibration-vibration energy transfer. J. Phys. Chem. B, 105 (28), 6716 6721. 

We study the vibrational energy redistribution and heat transport processes in solvated biomolecules. With this in mind, we construct, for classical calculations, appropriate initial conditions that mimic infrared or optical laser excitation of the system (Sections 7.2.1 and 7.2.2), and perform nonequilibrium MD simulations of the various relaxation processes (Section 7.2.3). 

Classical trajectories have been used to investigate vibrational energy transfer of vibrationally excited CS2, CH4, SFg, and SiF4 in collisions with various thermal molecules. The results show evidence for strong collisions (i.e., ones in which large amounts of energy are transferred) but the calculated probabilities ai e much lower than is usually assumed in theoretical treatments of unimolecular reactions in fact, the occurrence of such collisions is sufficiently low that they have little influence on the overall rate of relaxation. This method of successive collisions has also been used to study the relaxation of CS2 by H2, CO, HCl, CS2, and CH4. ... 

Hydron atoms readily dissolve into bulk Pd, where they can reside in either the sixfold octahedral or fourfold tetrahedral interstitial sites. Determine the classical and zero-point corrected activation energies for H hopping between octahedral and tetrahedral sites in bulk Pd. In calculating the activation energy, you should allow all atoms in the supercell to relax but, to estimate vibrational frequencies, you can constrain all the metal atoms. Estimate the temperature below which tunneling contributions become important in the hopping of H atoms between these two interstitial sites. 

Abstract A generalization of the Landau-Teller model for vibrational relaxation of diatoms in collisions with atoms at very low energies is presented. The extrapolation of the semiclassical Landau-Teller approach to the zero-energy Bethe-Wigner limit is based on the quasiclassical Landau method for calculation of transition probabilities, and the recovery of the Landau exponent from the classical collision time. The quantum suppression-enhancement probabilities are calculated for a general potential well, which supports several bound states, and for a Morse potential with arbitrary number of states. The model is applied to interpretation of quantum scattering calculations for the vibrational relaxation of H2 in collisions with He. 

Our recent electronic structure calculations 3deld a potential energy surface adequate to explain, at least qualitatively and within the uncertainties due to an incomplete knowledge of relaxation rates, the available experimental observations for the hydrogen-iodine reaction. The rate expressions, the rate constants, their temperature dependence, the vibrational excitation of HI products, the excitation and/or dissociation of reactant I2, the photochemical rates - all are compatible with the recent ab initio potential energy surface and with the classical trajectory calculations carried out with a similar surface. And all are compatible with either the bimolecular or termolecular mechanisms. It appears most likely that both mechanisms contribute, but the matter is not resolved as yet. 

We have also studied the overtone induced dissociation of HOOH by classical trajectory calculations using different Hamiltonians (12). Our results illustrate the importance of bending modes and provide evidence for incomplete relaxation of energy. The experimental data suggest a strong coupling of the torsional vibration to the HO stretch mode due to the dependence of the torsional barrier heights on the level of HO excitation, but the trajectory studies are not yet conclusive. The importance of rotation has been stressed by Sumpter and Thompson(12). 

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