Molecular structure of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mtext>H</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:mtext>O</mml:mtext></mml:mrow></mml:math>wetting layer on Pt(111)

Standop, Sebastian; Redinger, Alex; Morgenstern, Markus; Michely, Thomas; Busse, Carsten

doi:10.1103/physrevb.82.161412

Cited by 63 publications

(50 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As reported by Kimmel et al (36) and confirmed by our previous STM work (31), water deposited at 135-150 K onto Pt(111) first forms a one-molecule-thin wetting layer (37)(38)(39)(40). Then, isolated 3D ice crystallites emerge and eventually, at thicknesses of ∼3-10 nm, coalesce into a continuous multilayer film.…”

Section: Resultssupporting

confidence: 55%

Formation of hexagonal and cubic ice during low-temperature growth

Thürmer

Nie

2013

Proc. Natl. Acad. Sci. U.S.A.

110

View full text Add to dashboard Cite

From our daily life we are familiar with hexagonal ice, but at very low temperature ice can exist in a different structure--that of cubic ice. Seeking to unravel the enigmatic relationship between these two low-pressure phases, we examined their formation on a Pt (111) substrate at low temperatures with scanning tunneling microscopy and atomic force microscopy. After completion of the onemolecule-thick wetting layer, 3D clusters of hexagonal ice grow via layer nucleation. The coalescence of these clusters creates a rich scenario of domain-boundary and screw-dislocation formation. We discovered that during subsequent growth, domain boundaries are replaced by growth spirals around screw dislocations, and that the nature of these spirals determines whether ice adopts the cubic or the hexagonal structure. Initially, most of these spirals are single, i.e., they host a screw dislocation with a Burgers vector connecting neighboring molecular planes, and produce cubic ice. Films thicker than ∼20 nm, however, are dominated by double spirals. Their abundance is surprising because they require a Burgers vector spanning two molecular-layer spacings, distorting the crystal lattice to a larger extent. We propose that these double spirals grow at the expense of the initially more common single spirals for an energetic reason: they produce hexagonal ice.ice growth mechanisms | molecular surface steps | molecular-layer nucleation | scanning probe microscopy | spiral growth O wing to its ubiquity in nature, ice and its structural properties have inspired widespread interest (1, 2). Not long after the introduction of X-ray diffraction in 1912, the structure of the most common modification of ice, hexagonal ice Ih, had already been investigated extensively (1-6). In 1942, König (7) discovered that at low temperatures water occasionally crystallizes into a different modification, cubic ice Ic. Subsequently, cubic ice has been produced in the laboratory, e.g., by condensing water vapor onto cooled substrates (7-11), by heating amorphous solid water (7-9), by supercooling liquid water droplets (12-14) or clusters (15), or by freezing high-pressure phases of ice and reheating them at atmospheric pressure (16)(17)(18)(19). Cubic ice has been proposed to also occur naturally, e.g., in the earth's atmosphere (13,(20)(21)(22)(23)(24) and in comets (25,26). However, even after thousands of articles dedicated to ice formation have appeared, important questions regarding fundamental growth mechanisms of ice remain. Some of these questions concerning the competition between the two lowpressure crystalline phases ice Ih and ice Ic are addressed in this paper.Ice Ih and ice Ic have been observed to coexist at temperatures up to 240 K (10-12, 18, 27, 28). When ice Ic is heated above 170 K it transforms irreversibly into ice Ih. The release of a measurable amount of heat (on the order of 35 J/mol) (17-19) establishes hexagonal ice as the equilibrium structure above 170 K. Below 170 K no phase transformation has been observed, allowing for the poss...

show abstract

Section: Resultssupporting

confidence: 55%

Formation of hexagonal and cubic ice during low-temperature growth

Thürmer

Nie

2013

Proc. Natl. Acad. Sci. U.S.A.

110

View full text Add to dashboard Cite

show abstract

“…8 Our results show that in fact a sufficiently strong coupling to a surface with hexagonal symmetry is required to form a single hexagonal water layer, which obviously does not seem to be the case for water on Pt(111). 44,45 In order to understand the trends in the stability among the considered structures, it is crucial to analyze the factors determining the energetics. We find that what makes a particular water layer more stable cannot be attributed to a single factor.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Polymorphism of Water in Two Dimensions

Roman

Groß

2016

J. Phys. Chem. C

View full text Add to dashboard Cite

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. ...

show abstract

“…5,44,45 Such pentagon− hexagon−heptagon layers have been observed by STM on Pt(111), 5,45,46 Pd(111), 44 and Ni(111); 11 see Figure 3. This suggests that water structures on close-packed metal surfaces can be generated by constructing pentagon−hexagon− heptagon layers, drawing the curtain over the long-standing idea that water adopts an icelike structure.…”

Section: Accounts Of Chemical Researchmentioning

confidence: 85%

How Does Water Wet a Surface?

2015

View full text Add to dashboard Cite

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.

show abstract

Molecular structure of theH2Owetting layer on Pt(111)

Cited by 63 publications

References 24 publications

Formation of hexagonal and cubic ice during low-temperature growth

Formation of hexagonal and cubic ice during low-temperature growth

Polymorphism of Water in Two Dimensions

How Does Water Wet a Surface?

Contact Info

Product

Resources

About