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Abstract

We introduce bsmKinetic, an implementation of the stochastic multichannel point-transition approach to simulation of the charge transfer kinetics in molecular systems with reorganization of many intramolecular high-frequency vibrational mode in solvents with several relaxation timescales. The software provides simulation of the charge transfer kinetics in the molecular systems with many electronic states involved in photochemical transformations. It also allows simulating the charge transfer occurring in both equilibrium and nonequilibrium regimes. bsmKinetic is open-source software distributed under the terms of the GPL without additional components. Software is implemented on multiple computing platforms. It exploits Matsumoto and Nishimura source code for pseudorandom number generator and a hierarchy of custom parallelization of the stochastic trajectories built on MPI.

6. Concluding remarks

In this work we have presented the bsmKinetic code, that implements the stochastic multichannel point-transition approach to simulate charge transfer kinetics in solutions. A detailed description of the use of the code has been provided considering the example of intramolecular photoinduced electron transfer from the second electronic excited state of Zn–porphyrin to imide. The bsmKinetic is applicable to the description of the thermal and photoinduced charge transfer kinetics in systems with the reorganization of many intramolecular high-frequency vibrational mode in solvents with several relaxation timescales. It provides simulation of the kinetics in the molecular systems with many electronic states involved in photochemical transformations. Software allows simulating the electron transfer occurring in both equilibrium and nonequilibrium regimes. The nuclear nonequilibrium can be created by both pumping pulse and reaction itself. The model used has some limitations. The first is connected with the classical description of the solvent fluctuations so that their frequency have to be rather low that requires the inequality h¯/τi ≪ kBT to be fulfilled for each solvent relaxation mode. The second limitation of the model is caused by description of the vibronic states in terms of populations. This description ignores the quantum coherence and, hence, is applicable if only the electronic coherence lifetime, τc , is much shorter than the reaction time constant, 1/ket. This results in the inequality h¯/ √ 2ErmkBT ≪ 1/ket [27]. The inequality is met if the electron-solvent interaction is strong and the temperature is high. For Erm = 1 eV and the room temperature this leads to the inequality ket ≪ 1014 s −1 . The third limitation is connected with the usage of the diabatic basis. It requires the electronic couplings to be small. Roughly this results in the condition Vel < kBT [38].