Hong Sungyeon, Kim Donghun
Computational Science Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea.
J Phys Condens Matter. 2019 Nov 13;31(45):455403. doi: 10.1088/1361-648X/ab3820. Epub 2019 Aug 2.
Despite the amorphous nature of glassy water, x-ray or neutron scattering experiments reveal sharp peaks in the structure factor, indicating the existence of medium-range order (MRO) in the system. However the real space origin of the peaks has yet to be disclosed. Herein, we use a combined approach of molecular dynamics simulations and persistent homology (PH) to investigate two types of glassy water, low-density amorphous (LDA) and high-density amorphous (HDA) ices. We present prominent MRO ring structures in each type of the ices, distinguished by their size and shape as well as the number of their components: MRO rings in HDA are observed smaller, less planar and more membered, compared to those in LDA. The PH-extracted MRO rings successfully reproduce the quantitative features, including the position and width, of the first sharp diffraction peaks in the structure factor, hence suitably serving as the origin of experimental MRO signatures in the amorphous ices. Our study supports that PH is an effective tool to identify hidden MRO in amorphous configurations.
尽管玻璃态水具有非晶态的性质，但X射线或中子散射实验揭示了结构因子中的尖锐峰，这表明系统中存在中程有序（MRO）。然而，这些峰在实空间中的起源尚未被揭示。在此，我们使用分子动力学模拟和持久同调（PH）的组合方法来研究两种类型的玻璃态水，即低密度非晶态（LDA）冰和高密度非晶态（HDA）冰。我们在每种类型的冰中呈现出突出的MRO环结构，它们通过大小、形状以及组成部分的数量来区分：与LDA中的MRO环相比，HDA中的MRO环更小、更不平面且成员更多。PH提取的MRO环成功地再现了结构因子中第一个尖锐衍射峰的定量特征，包括位置和宽度，因此适合作为非晶态冰中实验MRO特征的起源。我们的研究支持PH是识别非晶态构型中隐藏MRO的有效工具。
