Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic and Center for Biomolecules and Complex Molecular Systems, 16610 Prague 6, Czech Republic.
Phys Chem Chem Phys. 2011 Nov 28;13(44):19960-9. doi: 10.1039/c1cp22238d. Epub 2011 Oct 13.
We present an Arrhenius analysis of self-diffusion on the prismatic surface of ice calculated from molecular dynamics simulations. The six-site water model of Nada and van der Eerden was used in combination with a structure-based criterion for determining the number of liquid-like molecules in the quasi-liquid layer. Simulated temperatures range from 230 K-287 K, the latter being just below the melting temperature of the model, 289 K. Calculated surface diffusion coefficients agree with available experimental data to within quoted precision. Our results indicate a positive Arrhenius curvature, implying a change in the mechanism of self-diffusion from low to high temperature, with a concomitant increase in energy of activation from 29.1 kJ mol(-1) at low temperature to 53.8 kJ mol(-1) close to the melting point. In addition, we find that the surface self-diffusion is anisotropic at lower temperatures, transitioning to isotropic in the temperature range of 240-250 K. We also present a framework for self-diffusion in the quasi-liquid layer on ice that aims to explain these observations.
我们提出了一种基于分子动力学模拟计算的冰棱柱面自扩散的阿仑尼乌斯分析。我们使用了 Nada 和 van der Eerden 的六点位水分子模型，并结合了一种基于结构的准则来确定准液态层中液态分子的数量。模拟温度范围从 230 K 到 287 K，后者略低于模型的熔点 289 K。计算出的表面扩散系数与可用的实验数据在给定的精度范围内一致。我们的结果表明阿仑尼乌斯曲线为正，这意味着自扩散机制从低温到高温发生了变化，激活能也随之从低温时的 29.1 kJ/mol 增加到接近熔点时的 53.8 kJ/mol。此外，我们还发现较低温度下表面自扩散具有各向异性，在 240-250 K 的温度范围内转变为各向同性。我们还提出了一个冰上准液态层自扩散的框架，旨在解释这些观察结果。
