近日，香港城市大学的曾晓成及其研究小组与美国宾夕法尼亚大学的Joseph S. Francisco以及北京师范大学的朱重钦等人合作并取得一项新进展。经过不懈努力，他们揭示纳米受限冰的富质子动力学和相行为。相关研究成果已于2024年1月22日在国际知名学术期刊《自然—物理学》上发表。

该研究团队探索了机器学习的潜力，并提供了纳米受限和高压下单层和双层冰的质子动力学，和相行为的大规模路径积分分子动力学模拟的证据。研究发现，二维冰的基础氢键网络的对称破缺和强核量子效应，是导致丰富的质子动力学的原因，例如二维冰内的超快一维质子跃迁。此外，研究人员还预测了十个二维冰相。值得注意的是，部分离子相和超离子相可以在较低压力下产生，这比先前测量或预测的压力低一个数量级。

此外，研究人员还观察到了二维固体熔化的行为，即从双层分子冰到塑性冰，再到六方相冰和超离子流体的连续双或三连续相变。

据悉，在地质、行星和生物环境以及纳米流体环境中，纳米孔中的水是普遍存在的。因此，从基础和应用的角度来看，理解高压条件下纳米受限水的相行为和质子动力学变得至关重要。

附：英文原文

Title: Rich proton dynamics and phase behaviours of nanoconfined ices

Author: Jiang, Jian, Gao, Yurui, Li, Lei, Liu, Yuan, Zhu, Weiduo, Zhu, Chongqin, Francisco, Joseph S., Zeng, Xiao Cheng

Issue&Volume: 2024-01-22

Abstract: Water confined in nanopores is ubiquitous in geological, planetary and biological environments and in nanofluidic settings. Understanding the phase behaviour and proton dynamics of nanoconfined water under high-pressure conditions is therefore important from both fundamental and applied points of view. Here we report a machine learning potential and present evidence from large-scale path-integral molecular dynamics simulations of the proton dynamics and phase behaviours of monolayer and bilayer ice under nanoconfinement and high pressures. We find that the symmetry breaking of the underlying hydrogen-bonding network of the two-dimensional (2D) ices together with strong nuclear quantum effects are responsible for the rich proton dynamics, such as the ultrafast one-dimensional proton-hopping within 2D ices. We also predict ten 2D ice phases. Notably, a 2D dynamic partially ionic phase and a superionic phase can be produced in the laboratory at pressures one order of magnitude lower than those measured for the bulk superionic phase or predicted for the partially ionic phase. We also identify a 2D solid-melting behaviour, namely consecutive double or triple continuous phase transitions from bilayer molecular ice to plastic ice and then to hexatic ice and the superionic fluid.

DOI: 10.1038/s41567-023-02341-8

Source: https://www.nature.com/articles/s41567-023-02341-8