：This paper presents a mesoscale numerical approach to investigate the chloride diffusivity in cracked concrete. Concrete is treated as a five-phase material, including cement paste, aggregate, interfacial transition zone (ITZ), crack, and damaged zone (DZ), for its heterogeneity. In the mesoscale model, the randomly distributed aggregates were treated as impermeable, whereas all other phases are assumed permeable but with different diffusion coefficients. It is assumed that the crack is located in the middle of the DZ, and there is a liner relationship of the chloride diffusion coefficients between the DZ and the crack. The developed mesoscale model is validated by comparing the simulation results with the experimental data. Finally, the influence of the DZ, such as the chloride diffusion coefficient, the width and length of the DZ, the width and length of the crack, on the penetration of chlorides in cracked concrete is examined and discussed.

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The recurrent neural network with the long short-term memory cell (LSTM-NN) is employed to simulate the long-time dynamics of open quantum systems. The bootstrap method is applied in the LSTM-NN construction and prediction, which provides a Monte Carlo estimation of a forecasting confidence interval. Within this approach, a large number of LSTM-NNs are constructed by resampling time-series sequences that were obtained from the early stage quantum evolution given by numerically exact multilayer multiconfigurational time-dependent Hartree method. The built LSTM-NN ensemble is used for the reliable propagation of the long-time quantum dynamics, and the simulated result is highly consistent with the exact evolution. The forecasting uncertainty that partially reflects the reliability of the LSTM-NN prediction is also given. This demonstrates the bootstrap-based LSTM-NN approach is a practical and powerful tool to propagate the long-time quantum dynamics of open systems with high accuracy and low computational cost.

The on-the-fly version of the symmetrical quasi-classical dynamics method based on the Meyer-Miller mapping Hamiltonian (SQC/MM) is implemented to study the nonadiabatic dynamics at conical intersections of polyatomic systems. The current on-the-fly implementation of the SQC/MM method is based on the adiabatic representation and the dressed momentum. To include the zero-point energy (ZPE) correction of the electronic mapping variables, we employ both the γadjusted and γ-fixed approaches. Nonadiabatic dynamics of the methaniminium cation (CH2NH2 + ) and azomethane are simulated using the on-the-fly SQC/MM method. For CH2NH2 + , both two ZPE correction approaches give reasonable and consistent results. However, for azomethane, the γ-adjusted version of the SQC/MM dynamics behaves much better than the γ-fixed version. The further analysis indicates that it is always recommended to use the γ-adjusted SQC/MM dynamics in the on-the-fly simulation of photoinduced dynamics of polyatomic systems, particularly when the excited-state is well separated from the ground state in the Franck-Condon region. This work indicates that the on-the-fly SQC/MM method is a powerful simulation protocol to deal with the nonadiabatic dynamics of realistic polyatomic systems.

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We carried out extensive studies to examine the performance of the fewest-switches surface hopping method in the description of the ultrafast intersystem crossing dynamic of various singlet-triplet (S-T) models by comparison with the results of the exact full quantum dynamics. Different implementation details and some derivative approaches were examined. As expected, it is better to perform the trajectory surface hopping calculations in the spin-adiabatic representation or by the local diabatization approach, instead of in the spin-diabatic representation. The surface hopping method provides reasonable results for the short-time dynamics in the S-T model with weak spin-orbital coupling (diabatic coupling), although it does not perform well in the models with strong spin-orbital coupling (diabatic coupling).When the system accesses the S-T potential energy crossing with rather high kinetic energy, the trajectory surface hopping method tends to produce the good description of the nonadiabatic intersystem crossing dynamics. The impact of the decoherence correction on the performance of the trajectory surface hopping is system dependent.It improves the result accuracy in many cases, while its influence may also be minor for other cases. a) zhenggang.

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