An unconventional bilayer ice structure on a NaCl(001) film

Chen, Ji; Guo, Jing; Meng, Xiangzhi; Peng, Jinbo; Sheng, Jiming; Xu, Limei; Jiang, Ying; Li, Xinzheng; Wang, Enge

doi:10.1038/ncomms5056

Cited by 72 publications

(71 citation statements)

References 47 publications

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“…58 Oxides and alkali halide surfaces provide often inhomogeneous adsorption sites, such as vacancy defects. Local probe measurements on nonmetallic surfaces are thus particular important and necessary to understand the influence of defects.…”

Section: ■ Beyond Metal Surfacesmentioning

confidence: 99%

How Does Water Wet a Surface?

2015

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The adsorption and reactions of water on surfaces has attracted great interest, as water is involved in many physical and chemical processes at interfaces. On metal surfaces, the adsorption energy of water is comparable to the hydrogen bond strength in water. Therefore, the delicate balance between the water-water and the water-metal interaction strength determines the stability of water structures. In such systems, kinetic effects play an important role and many metastable states can form with long lifetimes, such that the most stable state may not reached. This has led to difficulties in the theoretical prediction of water structures as well as to some controversial results. The direct imaging using scanning tunneling microscopy (STM) in ultrahigh vacuum at low temperatures offers a reliable means of understanding the local structure and reaction of water molecules, in particular when interpreted in conjunction with density functional theory calculations. In this Account, a selection of recent STM results on the water adsorption and dissociation on close-packed metal surfaces is reviewed, with a particular focus on Ru(0001). The Ru(0001) surface is one where water adsorbs intact in a metastable state at low temperatures and where partially dissociated layers are formed at temperatures above ∼150 K. First, we will describe the structure of intact water clusters starting with the monomer up to the monolayer. We show that icelike wetting layers do not occur on close-packed metal surfaces but instead hydrogen bonded layers in the form of a mixture of pentagonal, hexagonal, and heptagonal molecular rings are observed. Second, we will discuss the dissociation mechanism of water on Ru(0001). We demonstrate that water adsorption changes from dissociative to molecular as a function of the oxygen preadsorbed on Ru. Finally, we briefly review recent STM experiments on bulk ice (Ih and Ic) and water adsorption on insulating thin films. We conclude with an outlook illustrating the manipulation capabilities of STM in respect to probe the proton and hydrogen dynamics in water clusters.

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Section: ■ Beyond Metal Surfacesmentioning

confidence: 99%

How Does Water Wet a Surface?

2015

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“…It has long been assumed that water at flat surfaces tends to form hexagonal ice-like layers, 8 and only through the corrugation of the underlying substrate some other geometry might be imposed on the water layer. 4,9,10 Hence, the recent high-resolution electron microscopy observation of square ice confined between two graphene sheets 11 was rather surprising, as the water−graphene interaction possesses only a weak dependence on the position and orientation of the water molecule. 12,13 There is an ongoing discussion about whether or not the transmission electron microscopy images 11 should be attributed to a film of square water or to accumulated salt sandwiched between graphene sheets.…”

Section: ■ Introductionmentioning

confidence: 99%

Polymorphism of Water in Two Dimensions

Roman

Groß

2016

J. Phys. Chem. C

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The structure of interfacial water is governed by a delicate interplay between water−substrate and water−water interactions. In order to identify the structure-determining factors of ordered two-dimensional water, first calculations of free-standing water layers have been performed. We demonstrate that square bilayers, rhombic bilayers, truncated-square bilayers, and secondary-prism bilayers are energetically more favorable than the traditionally considered hexagonal bilayer. These two-dimensional water structures are stabilized by a combination of high coordination and optimum tetrahedral bonding geometry. The identified structuredetermining factors responsible for the polymorphism of water in two dimensions will be operative in any confined water structure. Graphene influence on the stability of water sheets is for the first time explicitly treated using first-principles electronic structure calculations, and changes in some ordered water structures due to non-negligible graphene−water interaction are described. ■ INTRODUCTIONInterfaces with water play important roles in many fields of natural sciences such as biology, (electro-)chemistry, materials science, and earth science. 1,2 While these solid−liquid interfaces are all around us, we still have not yet understood how interfacial water really behaves. What is clear is that the structure of water layers directly at the solid−liquid interface is governed by an interplay between the water−water and water− substrate interactions. 3,4 A basic understanding of the factors influencing the structure of the water layers is crucial for comprehending the function of water at interfaces, as interfacial water often exhibits properties that are distinctively different from those of bulk water. 5−7 Finding the most stable lowdimensional water polymorphs is an important step toward this fundamental understanding, since these systems provide benchmarks in which water−water interaction solely determines the structure and properties of interfacial water. It has long been assumed that water at flat surfaces tends to form hexagonal ice-like layers, 8 and only through the corrugation of the underlying substrate some other geometry might be imposed on the water layer. 4,9,10 Hence, the recent high-resolution electron microscopy observation of square ice confined between two graphene sheets 11 was rather surprising, as the water−graphene interaction possesses only a weak dependence on the position and orientation of the water molecule. 12,13 There is an ongoing discussion about whether or not the transmission electron microscopy images 11 should be attributed to a film of square water or to accumulated salt sandwiched between graphene sheets. 14,15 Still, this experimental study has raised interest in the fundamental question of whether under ambient conditions two-dimensional water layers can realize geometries that are not feasible for bulk ice. 16 All experimentally observed two-dimensional water structures are subject to water−substrate interactions that influence their shape. ...

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“…Confined and interfacial water-ice is ubiquitous in nature, playing an important role in a wide range of areas such as rock fracture, friction, and nanofluidics [1][2][3][4]. As a result of a delicate balance of forces (hydrogen bonding, van der Waals, and interaction with the confining material or substrate) confined and interfacial water forms a rich variety of structures [5][6][7][8][9][10]. Almost every specific system examined has revealed a different structure such as a 2D overlayer built from heptagons and pentagons on a platinum surface or the square ice observed within layers of graphene [8,10].…”

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confidence: 99%

Two Dimensional Ice from First Principles: Structures and Phase Transitions

et al. 2016

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Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here, we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression, the pentagonal structure becomes the most stable and persists up to ∼2 GPa, at which point the square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and the width.

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An unconventional bilayer ice structure on a NaCl(001) film

Cited by 72 publications

References 47 publications

How Does Water Wet a Surface?

How Does Water Wet a Surface?

Polymorphism of Water in Two Dimensions

Two Dimensional Ice from First Principles: Structures and Phase Transitions

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