Vibrational energy relaxation rates via the linearized semiclassical method without force derivatives

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Chemical Physics

Background:

• Vibrational energy relaxation is crucial for understanding molecular dynamics and chemical reactions.
• Existing computational methods, like the Shi-Geva scheme, have limitations in accuracy and input requirements.
• Accurate calculation of relaxation rates is essential for molecular simulations and predicting chemical behavior.

Purpose of the Study:

• To introduce a new, more accurate computational scheme for calculating vibrational energy relaxation rate constants.
• To overcome limitations of previous methods by employing a symmetrized force-force correlation function.
• To assess the computational feasibility and accuracy of the new scheme on benchmark models.

Main Methods:

• Applying the linearized semiclassical approximation to the symmetrized force-force correlation function.
• Avoiding power expansion of the initial force, thus eliminating the need for force derivatives.
• Testing the method on benchmark models, including nonpolar diatomic liquids.

Main Results:

• The new scheme demonstrates improved accuracy compared to the Shi-Geva method.
• The method successfully calculates vibrational energy relaxation rates for challenging systems like diatomic liquids.
• Performing the local harmonic approximation around the initial force configuration yields optimal agreement with experimental data.

Conclusions:

• The developed computational scheme offers a more accurate and robust approach for calculating vibrational energy relaxation rates.
• The method's accuracy is validated on diverse molecular systems, including nonpolar diatomic liquids.
• The choice of configuration for the local harmonic approximation significantly impacts the results, with the initial force configuration being optimal.