Density-Functional Tight-Binding Molecular Dynamics Simulations of Excess Proton Diffusion in Ice Ih, Ice Ic, Ice III, and Melted Ice VI Phases,The Journal of Physical Chemistry A

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Density-Functional Tight-Binding Molecular Dynamics Simulations of Excess Proton Diffusion in Ice Ih, Ice Ic, Ice III, and Melted Ice VI Phases
The Journal of Physical Chemistry A ( IF 2.7 ) Pub Date : 2017-12-29 00:00:00 , DOI: 10.1021/acs.jpca.7b10664
Aditya Wibawa Sakti , Yoshifumi Nishimura , Chien-Pin Chou , Hiromi Nakai _{1,

2}

Affiliation

The structural, dynamical, and energetic properties of the excess proton in ice were studied using density-functional tight-binding molecular dynamics simulations. The ice systems investigated herein consisted of low-density hexagonal and cubic crystalline variants (ice I_h and I_c) and high-density structures (ice III and melted ice VI). Analysis of the temperature dependence of radial distribution function and bond order parameters served to characterize the distribution and configuration of hundreds of water molecules in a unit cell. We confirmed that ice I_h and I_c possess higher hexagonal symmetries than ice III and melted ice VI. The estimated Grotthuss shuttling diffusion coefficients in ice were larger than that of liquid water, indicating a slower proton diffusion process in high-density structures than in low-density systems. The energy barriers calculated on the basis of the Arrhenius plot of diffusion coefficients were in reasonable agreement with experimental measurement for ice I_h. Furthermore, the energy barriers for high-density structures were several times larger than those of low-density systems. The simulation results were likely related to the suppression of proton transfer in disordered water configurations, in particular, ice with low hexagonal symmetry.

中文翻译：

在冰I _h，冰I _c，冰III和融化的冰VI相中过量质子扩散的密度函数紧密结合分子动力学模拟

使用密度泛函紧密结合分子动力学模拟研究了冰中过量质子的结构，动力学和能量性质。本文研究的冰系统由低密度六方和立方晶体变体（冰I _h和I _c）和高密度结构（冰III和融化的冰VI）组成。径向分布函数和键序参数对温度的依赖性分析有助于表征单位池中数百个水分子的分布和构型。我们确认冰I _h和I _c具有比冰III和融化的冰VI高的六角形对称性。在冰中估计的Grotthuss穿梭扩散系数大于液态水，表明高密度结构中的质子扩散过程比低密度系统中的慢。扩散系数的阿累尼乌斯曲线的基础上计算出的能量壁垒与实验测量冰我合理的协议_{^ h}。此外，高密度结构的能垒比低密度系统大几倍。模拟结果可能与抑制无序水结构中的质子转移有关，尤其是具有低六边形对称性的冰。

更新日期：2017-12-29

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