For a slow open quantum subsystem weakly coupled to a fast thermal bath, we derive the general form of the slippage to be applied to the initial conditions of the Redfield master equation. This slippage is given by a superoperator which describes the non-Markovian dynamics of the subsystem during the short-time relaxation of the thermal bath. We verify on an example that the Redfield equation preserves positivity after that the slippage superoperator has been applied to the initial density matrix of the subsystem. For δ-correlated baths, the Redfield master equation reduces to the Lindblad master equation and the slippage of initial conditions vanishes consistently.
The thermal transitions of confined polymers are important for the application of polymers in molecular scale devices and advanced nanotechnology. However, thermal transitions of ultrathin polymer assemblies confined in subnanometre spaces are poorly understood. In this study, we show that incorporation of polyethylene glycol (PEG) into nanochannels of porous coordination polymers (PCPs) enabled observation of thermal transitions of the chain assemblies by differential scanning calorimetry. The pore size and surface functionality of PCPs can be tailored to study the transition behaviour of confined polymers. The transition temperature of PEG in PCPs was determined by manipulating the pore size and the pore–polymer interactions. It is also striking that the transition temperature of the confined PEG decreased as the molecular weight of PEG increased.
The performance increase of the lithium-ion
battery (LIB) is critical for effectively leveling the cyclic nature
of renewable energy sources related to the global warming. The current
LIB performance with liquid electrolytes, e.g., ethylene carbonate
(EC) and propylene carbonate (PC), is strongly dependent on a stable
solid electrolyte interphase (SEI) films on the electrode surfaces.
However, such electrolyte-dependent SEI film formation still remains
not-fully understood. To investigate its microscopic characteristics,
we have performed the atomistic reaction simulations with the recently
developed hybrid Monte Carlo (MC)/molecular dynamics (MD) reaction
method, and have exposed for the first time the atomistic picture
of the structure of the SEI films consistent with the experimental
evidence and conjectures. It was also found that the dense EC-based
SEI film can protect electrolyte from the reduction, providing the
cavities which have sufficient size for passing of Li+ cations.
In contrast, the PC-based one became sparser, and is reasonably expected
not to protect the electrolyte from reductive decomposition due to
the presence of methyl group of PC, which prevents the stable aggregation
of reaction products. Finally, it was concluded that the SEI film
formation is strongly sensitive to the small structural difference
of electrolyte molecules at the microscopic level.
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