The influence of the quencher concentration on the rate of simple bimolecular reaction: Molecular dynamics study.

The paper presents the results of large-scale molecular dynamics simulations of the irreversible bimolecular reaction A+B→C+B for the simple liquid composed of mechanically identical soft spheres. The systems with the total number of molecules corresponding to 10⁷–10⁹ are considered. The influence of the concentration of a quencher (B) on the surviving probability of A and the reaction rate is analyzed for a wide range of the concentrations and for two significantly different reduced densities. It is shown that the quencher concentration dependence effect (QCDE) is, in fact, a composition of two QCDE effects: the short-time QCDE that increases the reaction rate and the long-time QCDE that decreases it. The paper also analyzes the influence of the concentration on the steady-state rate constant, k_SS, obtained by integrating the surviving probability. The excess in k_SS due to finite quencher concentration changes the sign from negative to positive while going from low to high concentrations. Generally, the excess is extremely weak. It attains a 1% level only if the concentration is very high. [ABSTRACT FROM AUTHOR]