Surface Crystallization in a Liquid AuSi Alloy

Shpyrko, Oleg; Streitel, Reinhard; Balagurusamy, Venkat; Grigoriev, Alexei; Deutsch, Moshe; Ocko, B. M.; Meron, Mati; Lin, Binhua; Pershan, Peter S.

doi:10.1126/science.1128314

Cited by 192 publications

(206 citation statements)

References 27 publications

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“…For instance, it is known that several materials, such as normal alkanes (11), alcohols (12), and certain alloys (13), can undergo surface freezing. However, it is not yet known with predictive certainty what makes a material susceptible to surface-induced crystallization.…”

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confidence: 99%

Computational investigation of surface freezing in a molecular model of water

Haji-Akbari

Debenedetti

2017

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

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Water freezes in a wide variety of low-temperature environments, from meteors and atmospheric clouds to soil and biological cells. In nature, ice usually nucleates at or near interfaces, because homogenous nucleation in the bulk can only be observed at deep supercoolings. Although the effect of proximal surfaces on freezing has been extensively studied, major gaps in understanding remain regarding freezing near vapor-liquid interfaces, with earlier experimental studies being mostly inconclusive. The question of how a vapor-liquid interface affects freezing in its vicinity is therefore still a major open question in ice physics. Here, we address this question computationally by using the forward-flux sampling algorithm to compute the nucleation rate in a freestanding nanofilm of supercooled water. We use the TIP4P/ice force field, one of the best existing molecular models of water, and observe that the nucleation rate in the film increases by seven orders of magnitude with respect to bulk at the same temperature. By analyzing the nucleation pathway, we conclude that freezing in the film initiates not at the surface, but within an interior region where the formation of doublediamond cages (DDCs) is favored in comparison with the bulk. This, in turn, facilitates freezing by favoring the formation of nuclei rich in cubic ice, which, as demonstrated by us earlier, are more likely to grow and overcome the nucleation barrier. The films considered here are ultrathin because their interior regions are not truly bulk-like, due to their subtle structural differences with the bulk.ice | nucleation | molecular simulations | surface freezing | statistical mechanics F reezing of water into ice is ubiquitous in nature and can occur in a wide range of environments, from biological cells (1) and soil (2) to meteors (3) and atmospheric clouds (4). Ice formation is particularly important in the atmospheric processes that exert a major influence on our weather and climate. Indeed, the radiative properties (4) and precipitation propensity (5) of a cloud are both determined by the amount of ice that it harbors. Not surprisingly, the liquid fraction of clouds is an extremely important input parameter in meteorological models (6). Freezing is a first-order phase transition and proceeds through a mechanism known as nucleation and growth. In mixed-phase clouds, which are responsible for the bulk of land surface precipitation (7), freezing is usually nucleationlimited, and individual freezing events are rare. Predicting the timing of such rare freezing events is important in modeling cloud microphysics. However, nucleation rates, which are volume-or area-normalized inverse nucleation times, can only be measured experimentally over a narrow range of temperatures and pressures (8), and extrapolations to other temperatures are nontrivial (9). In nature, homogeneous nucleation of ice is only likely at very low temperatures, and the majority of freezing events in mixed-phase clouds occur heterogeneously, at interfaces provided by external insol...

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confidence: 99%

Computational investigation of surface freezing in a molecular model of water

Haji-Akbari

Debenedetti

2017

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

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“…Si) and crystal structures. [2][3][4][5][6] More recently, a stable two-dimensional (2D) gold silicide has been evidenced following surface crystallisation of the eutectic Au 82 Si 18 liquid above the eutectic temperature T E ¼ 359 C. 7 It was shown to have an Au 4 Si 8 composition and a rectangular crystal structure, stable up to 371 C. 8 This 2D crystalline silicide phase has also been obtained under ultra high vacuum (UHV) conditions following deposition of a 3 nm Au layer on a Si(100) substrate and subsequent annealing above the eutectic temperature (T E ). 9 Other Au/Si alloys were also obtained in UHV conditions either at room temperature (RT) [10][11][12] or by annealing thicker Au films (10-100 nm) deposited on a Si substrate.…”

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Adsorption of silicon on Au(110): An ordered two dimensional surface alloy

Enriquez

Mayne

Kara

et al. 2012

Applied Physics Letters

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We report on experimental evidence for the formation of a two dimensional Si/Au(110) surface alloy. In this study, we have used a combination of scanning tunneling microscopy, low energy electron diffraction, Auger electron spectroscopy, and ab initio calculations based on density functional theory. A highly ordered and stable Si-Au surface alloy is observed subsequent to growth of a sub-monolayer of silicon on an Au (110)

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“…2,3 Recent experimental studies have shown marked differences between the two systems, however. Whereas eutectic Au-Si exhibits a liquid surface structure with strong Si surface enrichment and planar ordering, 4 this is not observed in eutectic Au-Ge. 5 The coordinations in the eutectics also show differences.…”

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confidence: 93%

“…5 The coordinations in the eutectics also show differences. 6 Recently, it was predicted that a compound Au 4 Si could exist in Au-Si ͑Ref. 7͒ in spite of it being known as a noncompound-forming system.…”

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confidence: 99%

Existence of a stable compound in the Au-Ge alloy system

et al. 2010

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First-principles electronic structure calculations predict the existence of a crystalline compound in the Au-Ge system. The structure is found by matching the theoretically determined local atomic structure in the liquid state with that for experimentally known crystal structures in other alloys. Subsequently, the best matching crystalline structures were structurally optimized using first-principles methods. Surprisingly, although Au-Ge is known as a non-compound-forming system, a crystal structure was found to be more stable than the terminal phases by about 6 meV/atom at T = 0 K. Possibly, this structure can be prepared by a suitably chosen substrate such as Pt 5 P 2 .

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Surface Crystallization in a Liquid AuSi Alloy

Cited by 192 publications

References 27 publications

Computational investigation of surface freezing in a molecular model of water

Computational investigation of surface freezing in a molecular model of water

Adsorption of silicon on Au(110): An ordered two dimensional surface alloy

Existence of a stable compound in the Au-Ge alloy system

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