北京大学江颖团队报道了冰表面结构和预融化的原子分辨率成像。相关研究成果发表在2024年5月22日出版的《自然》果。

冰的表面与许多物理和化学性质密切相关，如融化、冻结、摩擦、气体吸收和大气反应。尽管进行了广泛的实验和理论研究，但由于脆弱的氢键网络和复杂的预融化过程，冰界面的确切原子结构仍然难以捉摸。

该文中，研究人员通过使用具有一氧化碳功能化尖端的基于qPlus的低温原子力显微镜，实现了六方水冰（ice Ih）的基础（0001）表面结构的原子分辨率成像。研究发现，结晶冰Ih表面由Ih和立方（Ic）堆叠的混合纳米畴组成，形成√19×√19周期性超结构。密度泛函理论表明，这种重建的表面在理想的冰面上是稳定的，主要是通过最小化悬挂的OH键之间的静电排斥。

此外，研究人员观察到，随着温度的升高（高于120K），冰表面逐渐变得无序，这表明预融化过程的开始。表面预融化发生在Ih和Ic畴之间的缺陷边界，并且可以通过形成平面局部结构来促进。这些结果结束了关于冰表面结构的长期争论，并揭示了冰预融化的分子起源，这可能导致对冰物理和化学理解的范式转变。

附：英文原文

Title: Imaging surface structure and premelting of ice Ih with atomic resolution

Author: Hong, Jiani, Tian, Ye, Liang, Tiancheng, Liu, Xinmeng, Song, Yizhi, Guan, Dong, Yan, Zixiang, Guo, Jiadong, Tang, Binze, Cao, Duanyun, Guo, Jing, Chen, Ji, Pan, Ding, Xu, Li-Mei, Wang, En-Ge, Jiang, Ying

Issue&Volume: 2024-05-22

Abstract: Ice surfaces are closely relevant to many physical and chemical properties, such as melting, freezing, friction, gas uptake and atmospheric reaction1,2,3,4,5,6,7,8. Despite extensive experimental and theoretical investigations9,10,11,12,13,14,15,16,17, the exact atomic structures of ice interfaces remain elusive owing to the vulnerable hydrogen-bonding network and the complicated premelting process. Here we realize atomic-resolution imaging of the basal (0001) surface structure of hexagonal water ice (ice Ih) by using qPlus-based cryogenic atomic force microscopy with a carbon monoxide-functionalized tip. We find that the crystalline ice-Ih surface consists of mixed Ih- and cubic (Ic)-stacking nanodomains, forming √19×√19 periodic superstructures. Density functional theory reveals that this reconstructed surface is stabilized over the ideal ice surface mainly by minimizing the electrostatic repulsion between dangling OH bonds. Moreover, we observe that the ice surface gradually becomes disordered with increasing temperature (above 120Kelvin), indicating the onset of the premelting process. The surface premelting occurs from the defective boundaries between the Ih and Ic domains and can be promoted by the formation of a planar local structure. These results put an end to the longstanding debate on ice surface structures and shed light on the molecular origin of ice premelting, which may lead to a paradigm shift in the understanding of ice physics and chemistry.

DOI: 10.1038/s41586-024-07427-8

Source: https://www.nature.com/articles/s41586-024-07427-8