Mean first-passage times for solvated LiCN isomerization at intermediate to high temperatures

TL;DR

This paper investigates the temperature-dependent isomerization of LiCN using stochastic dynamics, revealing the Kramers turnover and comparing reaction rate methods across temperature regimes.

Contribution

It demonstrates the application of Langevin dynamics and MFPTs to observe the Kramers turnover and compares these with PGH rates at various temperatures.

Findings

Kramers turnover observed at intermediate and high temperatures.

Reaction rates follow a square root behavior at high temperatures.

Good agreement between MFPT and PGH methods at lower temperatures.

Abstract

The behavior of a particle in a solvent has been framed using stochastic dynamics since the early theory of Kramers. A particle in a chemical reaction reacts slower in a diluted solvent because of the lack of energy transfer via collisions. The flux-over-population reaction rate constant rises with increasing density before falling again for very dense solvents. This Kramers turnover is observed in this paper at intermediate and high temperatures in the backward reaction of the LiNC $\rightleftharpoons$ LiCN isomerization via Langevin dynamics and mean first-passage times (MFPTs). It is in good agreement with the Pollak-Grabert-H\"anggi (PGH) reaction rates at lower temperatures. Furthermore, we find a square root behavior of the reaction rate at high temperatures and have made direct comparisons of the methods in the intermediate- and high- temperature regimes; all suggesting increased ranges in accuracy of both the PGH and MFPT approaches.