Simulation study for adsorption-induced structural transition in stacked-layer porous coordination polymers: Equilibrium and hysteretic adsorption behaviors
Simulation study for adsorption-induced structural transition in stacked-layer porous coordination polymers: Equilibrium and hysteretic adsorption behaviors
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DOI：
10.1063/1.4789810
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发表时间：
2013-02-07
影响因子：
4.4
通讯作者：
Miyahara, Minoru T.
中科院分区：
文献类型：
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作者：
Numaguchi, Ryohei;Tanaka, Hideki;Miyahara, Minoru T.
我们对堆积层多孔配位聚合物的简化模型进行了宏正则蒙特卡罗模拟和自由能分析，以理解栅极现象，这是由客体粒子吸附引起的主体骨架的结构转变。我们的计算表明，在热力学平衡下，客体吸附使体系稳定，导致主体形变。我们还研究了自发跃迁行为(亚稳态条件下的门的打开和关闭)。当使用自由能分析确定的所需激活能与系统能量涨落相等时，应该发生结构转变。为了估计系统的能量起伏，我们基于过渡态理论建立了一个动力学跃迁模型。在该模型中，可以通过设置主体骨架的吸附时间和过渡区大小来计算体系的能量涨落。该模型表明，较小的磁区尺寸会在较低的压强下产生开闸转变。此外，我们还揭示了平衡结构转变压力与倒易温度的对数斜率呈现出转变热，而开关门转变压力与倒易温度的斜率呈现出活化热。(C)2013年美国物理研究所。[http://dx.doi.org/10.1063/1.4789810]
We conduct grand canonical Monte Carlo simulations and a free-energy analysis for a simplified model of a stacked-layer porous coordination polymer to understand the gate phenomenon, which is a structural transition of a host framework induced by the adsorption of guest particles. Our calculations demonstrate that stabilization of the system due to the guest adsorption causes host deformation under thermodynamic equilibrium. We also investigate spontaneous transition behaviors (gate opening and closing under metastable conditions). The structural transition should occur when the required activation energy, which is determined using the free-energy analysis, becomes equal to the system energy fluctuation. To estimate the system energy fluctuation, we construct a kinetic transition model based on the transition state theory. In this model, the system energy fluctuation can be calculated by setting the adsorption time and transition domain size of the host framework. The model demonstrates that a smaller domain size results in a gate-opening transition at lower pressure. Furthermore, we reveal that the slope of the logarithm of the equilibrium structural transition pressure versus reciprocal temperature shows transition enthalpy, and that slopes of the gate-opening and -closing transition pressures versus reciprocal temperature show activation enthalpies. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789810]