Cubic Ice Research Articles

Path Integral Molecular Dynamics Simulation on Atomic Distribution in Amorphized Ice Ic

We have investigated the effects of compression and quantization on atomic distribution in ice Ic and in its compressed states at 77 K and 10 K, using the path integral molecular dynamics (PIMD) simulations over wide range of volume. It has been found that the high density amorphous ice (HDA) is attained by compression but volume range to retain ice structure is wider at 10 K than 77 K. We have discovered that quantum dispersion of atoms in ice Ic at 10 K induces non-zero probability that hydrogen-bonded H2O molecular molecules are oriented nonlinearly in the crystal structure, which was believed to contain exclusively linear orientation of hydrogen-bonded molecular pairs in this ice. It has been found that for HDA there is each non-zero probability of orientational disorder of hydrogen-bonded H2O pairs, of such uniform distribution of H atoms as observed in supercritical fluids in general, and of H atoms located at the O-O midpoint. The present PIMD simulations have revealed that these observed anomalous characteristics of atomic distribution in HDA are caused by both quantization of atoms and compression of the system.

Dislocation mechanism for transformation between cubic ice Ic and hexagonal ice Ih

Cubic ice Ic is metastable, yet can form by the freezing of supercooled water, vapour deposition at low temperatures and by depressurizing high-pressure forms of ice. Its structure differs from that of common hexagonal ice Ih in the order its molecular layers are stacked. This stacking order, however, typically has considerable disorder; that is, not purely cubic, but alternating in hexagonal and cubic layers. In time, stacking-disordered ice gradually decreases in cubicity (fraction having cubic structure), transforming to hexagonal ice. But, how does this disorder originate and how does it transform to hexagonal ice? Here we use numerical data on dislocations in hexagonal ice Ih to show that (1) stacking-disordered ice (or Ic) can be viewed as fine-grained polycrystalline ice with a high density of extended dislocations, each a widely extended stacking fault bounded by partial dislocations, and (2) the transformation from ice Ic to Ih is caused by the reaction and motion of these partial dislocations. Moreover, the stacking disorder may be in either a higher stored energy state consisting of a sub-boundary network arrangement of partial dislocations bounding stacking faults, or a lower stored energy state consisting of a grain structure with a high density of stacking faults, but without bounding partial dislocations. Each state transforms to Ih differently, with a duration to fully transform that strongly depends on temperature and crystal grain size. The results are consistent with the observed transformation rates, transformation temperatures and wide range in heat of transformation.

Competition between ices Ih and Ic in homogeneous water freezing.

The role of cubic ice, ice Ic, in the nucleation of ice from supercooled water has been widely debated in the past decade. Computer simulations can provide insightful information about the mechanism of ice nucleation at a molecular scale. In this work, we use molecular dynamics to study the competition between ice Ic and hexagonal ice, ice Ih, in the process of ice nucleation. Using a seeding approach, in which classical nucleation theory is combined with simulations of ice clusters embedded in supercooled water, we estimate the nucleation rate of ice for a pathway in which the critical nucleus has an Ic structure. Comparing our results with those previously obtained for ice Ih [Sanz et al., J. Am. Chem. Soc. 135, 15008 (2013)], we conclude that within the accuracy of our calculations both nucleation pathways have the same rate for the studied water models (TIP4P/Ice and TIP4P/2005). We examine in detail the factors that contribute to the nucleation rate and find that the chemical potential difference with the fluid, the attachment rate of particles to the cluster, and the ice-water interfacial free energy are the same within the estimated margin of error for both ice polymorphs. Furthermore, we study the morphology of the ice clusters and conclude that they have a spherical shape.

How Does Water Wet a Surface?

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.

Dielectric Anomalies in Crystalline Ice: Indirect Evidence of the Existence of a Liquid–Liquid Critical Point in H2O

The phase diagram of H2O is extremely complex, in particular, it is believed that a second critical point exists deep below the supercooled water (SCW) region where two liquids of different densities coexist. The problem however, is that SCW freezes at temperatures just above this hypothesized liquid-liquid critical point (LLCP) so direct experimental verification of its existence has yet to be realized. Here, we report two anomalies in the complex dielectric constant during warming in the form of a peak anomaly near Tp=203 K and a sharp minimum near Tm=212 K from ice samples prepared from SCW under hydrostatic pressures up to 760 MPa. The same features were observed about 4 K higher in heavy ice. Tp is believed to be associated to the nucleation process of metastable cubic ice Ic and Tm the transitioning of ice Ic to either ices Ih or II depending on pressure. Given that Tp and Tm are nearly isothermal and present up to at least 620 MPa and ending as a critical point near 33-50 MPa, it is deduced that two types of SCW with different density concentrations exists which affects the surface energy of ice Ic nuclei in the "no man's land" region of the phase diagram. Our results are consistent with the LLCP theory and suggest that a metastable critical point exists in the region of 33-50 MPa and Tc > 212 K.

15. Control of ice formation in biological samples

Lowering the temperature of a biological sample reduces the pace of biochemical metabolism and ultimately stops it altogether. This process, in combination with rewarming the sample with minimal tissue damage, is the essence of cryopreservation. A key obstacle to successful cryopreservation is that, as the biological material is cooled, liquid water within the sample may reorganize into a more stable, crystalline form, namely ice. Such crystallization can be devastating for several reasons: it disrupts the structure of membranes, reduces the water content of solutions, and induces mechanical and possibly electrical stresses. Below I list several factors that are relevant to ice formation during cryopreservation, and outline methods and ideas on how to control it. Under the conditions relevant to cryobiology, ice has an open structure with hexagonal symmetry (ice Ih) or, under some conditions, cubic symmetry (ice Ic). As water freezes its volume increases, which can create high pressure in tissues. In addition, gases and solutes are excluded from the ice matrix during freezing, leading to gas bubble formation and to high solute concentrations in the surrounding solution and hence to osmotic stress on cells. The surface energy of an ice crystal plays an important role in its stability. The melting point shifts to lower temperature as the crystal surface curvature increases. This melting point shift drives recrystallization of ice in which small crystals melt while bigger crystals grow at the same temperature, a process that promotes increasingly large ice crystals that are harmful to cells. Because crystals smaller than a certain size cannot grow at a given temperature, water can be supercooled to below its equilibrium melting temperature without nucleation of ice crystals. The equilibrium melting temperature is also influenced by solutes in the water that reduce the water chemical potential and thus lower the melting temperature of the ice. Moreover, because ice crystal growth depends of the diffusion of water molecules to the crystal surface, another important factor is the viscosity of water, which increases with decreasing temperature and increasing solute concentration. Several methods are used, or have been suggested, to control ice growth. First, solutes reduce the melting point and increase the viscosity of a solution, thus reducing the nucleation rate. At high enough concentrations, solutes can lead to vitrification where the solution solidifies into an amorphous solid without crystallization. Alternatively, controlled nucleation—in which nucleation is selectively induced by ice nucleation proteins, electrofreezing, sonication in addition to local cooling—can be implemented to maintain a moderate supercooling while avoiding internal nucleation of ice in cells. In addition, unidirectional solidification can control the build-up of pressure in samples. High pressure methods can lower the melting point, and reduce nucleation rates. Rapid warming is used to avoid ice growth during devitrification and recrystallization. In addition, ice-binding proteins and other ice-active materials can influence ice growth by directly interacting with ice. In this way they inhibit the recrystallization and growth of ice, and influence ice nucleation. A hurdle approach, in which a combination of methods to control ice growth is utilized, will probably prove to be the optimal method for the fine control of ice in cryopreservation.

Homogeneous nucleation of predominantly cubic ice confined in nanoporous alumina.

The nucleation mechanism of water can be precisely regulated by confinement within nanoporous alumina. We found a transition from heterogeneous nucleation of hexagonal ice (Ih) to homogeneous nucleation of predominantly cubic ice (Ic) with decreasing pore diameter. These results lead to a phase diagram of water under confinement. It contains a (stable) predominant Ic form, a form known to exist only in the upper atmosphere. Possible applications range from cryopreservation to construction materials like cement.

Approximations to the full description of stacking disorder in ice I for powder diffraction

Abstract Different descriptions of the stacking disorder of the so-called “cubic” phase “ice Ic” and stacking-faulted hexagonal ice Ih exist. We present an overview of the effect of different stacking disorder interaction ranges s from s = 2 to s = 4 after Jagodzinski on the (neutron) powder diffraction patterns of stacking-disordered ice I, which we propose to name ice Ich. We fit in a systematic approach simulated diffraction data of ice Ich for s up to 4 with a multi-peak approach. In this way we allow for estimating the relative proportion of cubic sequences in the stacking sequences by using readily accessible observables of a diffraction pattern.

19. YYzyilin Baainda Osmanli Adliye Teekilatinin Yenilenme SSrecine Medeniyet Algisinin Etkisi (Perception of Civilization's Impact on the Reconstruction of Ottoman Judicial Organization at the Beginning of the 19th Century)

Turkish Abstract: Osmanli Devleti 19. Yuzyilin basinda hemen her kurumunda yenilik/reform hareketi baslatmistir. Bu hareketler kisa sure sonra Batililasma istegine donusmustur. Eski gunlere geri donme arayislari icinde, en sonunda “Bati gibi olmak zorundayiz” seklinde ozetlenen bir politika benimsenmistir. Bati’nin geldigi medeniyet seviyesine gelmenin, kurtulusun anahtari olacagini savunan devlet adamlarinin onculugunde, hemen her padisah, Bati medeniyetinin ulasmis oldugu seviyeye gelme arzusuyla, birtakim reformlar yapmistir. Bu dogrultuda Bati’dan bilim adamlari getirtilmis, Bati’yi gozlemlemesi icin devlet adamlari yurt disina gonderilmis, elci ve diplomatlardan raporlar hazirlamalari istenmis, Bati medeniyeti ithal edilmis, Batili devlet adamlarinin ve ulke icindeki elci ve diplomatlarin gorusleri dikkate alinmis ve en nihayetinde devletin yonu Bati’ya cevrilmistir. Batililasma, medeni olmayla esanlamli gorulmus ve yapilan yeniliklerle Bati’nin ulasmis oldugu seviyeye gelebilmek hedeflenmistir. 19. yuzyil reformlari tek tek incelendiginde, Bati’nin etkili oldugu veya Bati eksenli bir anlayis goze carpar. Boylece Bati medeniyetinde ortaya cikan insan haklari, yasama, mulkiyet ve haysiyet gibi kavramlarin, ozgurluk ve hurriyet kavramlariyla ic ice gectigi bir ortamda gerceklestirilmesine yonelik bir ideal ortaya cikmistir. Reform yanlisi devlet adamlarinin, medeniyetin olcusu olarak kabul ettikleri Avrupa toplumuna benzeme ideali olan Avrupalilasma ise, zaman zaman Batililasma yerine kullanilmistir. Bununla birlikte Avrupalilasma, medeniyet seviyesi ileri kabul edilen Bati’ya ve dolayisiyla Bati hukukuna dâhil olma cabasidir. Avrupalilasma, bu yonuyle 1815 Viyana Kongresi’nde dile getirilen “Avrupa Uyumu” projesinin kabul gormesinin ardindan hukukta da bir uyum saglama dusuncesinden kaynaklanmis bir kavram olarak yenilenme surecine dahil olmustur. Bu arastirmada Osmanli Adliye Teskilatinin yenilenme surecinde, medeniyet algisinin ne denli etkili oldugu, medeniyet algisina etki eden faktorlerin analizi ve 19. Yuzyil siyasi gelismeleriyle birlikte degerlendirilecektir.English Abstract: Ottoman Empire has begun innovations/reform movement in almost all institutions at the beginning of the 19th century. This movement soon turned into Westernization request. A policy that has been adopted summarized as we have to be like the West” in the quest to return to the old days, in the end. Almost every Sultan has made some reforms, with the desire to come to the level of Western civilization, under the leadership of statesmen argues that the key to salvation should be like Western civilization. In this respect, scientists have been brought from the West, statesmen were sent abroad to observe the West, were asked to prepare reports by ambassadors and diplomats, Western civilization has been imported, are considered opinions of Western statesmen and ambassadors and diplomats in the country,and ultimately the direction of the state is translated to the West. Westernization, has been seen as synonymous with be civilized and is aimed to come the level of the West have reached. When examined individually reforms of the 19th century, are noticeable West to be effective or an understanding of the Western axis. Thus has emerged an ideal for carrying with emerging concepts in Western civilization such as human rights, legislative property and dignity, are intertwined with concepts such as liberty and freedom. Europeanization reformminded statesmen, they accept as a measure of civilization is the ideal of society look like. was used in place Westernization from time to time. However, Europeanization is an effort that adopted advanced level of civilization in the West and therefore Western law to be involved. Europeanization has been included in renewal process as a concept stemmed also from the idea to adapt in law after acceptance of Project expressed at the Congress of Vienna in 1815 as European Integration. In this study, will be assessed that analysis of factors affecting the perception of civilization and political developments of the 19th century with how effective is the perception of civilization, in the process of renewal of the Ottoman Courthouse Organization.

Crystallization of confined water pools with radii greater than 1 nm in AOT reverse micelles.

Freezing of water pools inside aerosol sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles has been investigated. Previous freezing experiments suffer from collision and fusion of AOT micelles and resultant loss of water from the water pool by shedding out during the cooling process. These phenomena have restricted the formation of ice to only when the radius of the water pool (Rw) is below 1 nm, and only amorphous ice has been observed. To overcome the size limitation, a combination of rapid cooling and a custom-made cell allowing thin sample loading is applied for instantaneous and homogeneous freezing. The freezing process is monitored with attenuated total reflection infrared spectroscopy (ATR-IR) measurements. A cooling rate of ca. -100 K/min and a sample thickness of ca. 50 μm overcomes the limitations mentioned above and allows the crystallization of water pools with larger radii (Rw > 1 nm). The corresponding ATR-IR spectra of the frozen water pools with Rw < 2.0 nm show similar features to the spectrum of metastable cubic ice (Ic). Further increase of the radius of the water pool (Rw > 2.0 nm), unfortunately, drastically decreased the integrated area of the ν(OH) band observed just after freezing, indicating the breakup of the micellar structure and shedding out of the water pool. In addition, it was revealed that Ic ice can also be formed in flexible organic self-assembled AOT reverse micelles for at least Rw ≤ ca. 2 nm, as well as in inorganic and solid materials with a pore radius of ca. 2 nm. The dependence of the phase transition temperature on the curvature of the reverse micelles is discussed from the viewpoint of the Gibbs-Thomson effect.

New metastable form of ice and its role in the homogeneous crystallization of water.

The homogeneous crystallization of water at low temperature is believed to occur through the direct nucleation of cubic (Ic) and hexagonal (Ih) ices. Here, we provide evidence from molecular simulations that the nucleation of ice proceeds through the formation of a new metastable phase, which we name Ice0. We find that Ice0 is structurally similar to the supercooled liquid, and that on growth it gradually converts into a stacking of Ice Ic and Ih. We suggest that this mechanism provides a thermodynamic explanation for the location and pressure dependence of the homogeneous nucleation temperature, and that Ice0 controls the homogeneous nucleation of low-pressure ices, acting as a precursor to crystallization in accordance with Ostwald's step rule of phases. Our findings show that metastable crystalline phases of water may play roles that have been largely overlooked.

Proton Ordering of Cubic Ice Ic: Spectroscopy and Computer Simulations.

Several proton-disordered crystalline ice structures are known to proton order at sufficiently low temperatures, provided that the right preparation procedure is used. For cubic ice, ice Ic, however, no proton ordering has been observed so far. Here, we subject ice Ic to an experimental protocol similar to that used to proton order hexagonal ice. In situ FT-IR spectroscopy carried out during this procedure reveals that the librational band of the spectrum narrows and acquires a structure that is observed neither in proton-disordered ice Ic nor in ice XI, the proton-ordered variant of hexagonal ice. On the basis of vibrational spectra computed for ice Ic and four of its proton-ordered variants using classical molecular dynamics and ab initio simulations, we conclude that the features of our experimental spectra are due to partial proton ordering, providing the first evidence of proton ordering in cubic ice. We further find that the proton-ordered structure with the lowest energy is ferroelectric, while the structure with the second lowest energy is weakly ferroelectric. Both structures fit the experimental spectral similarly well such that no unique assignment of proton order is possible based on our results.

Interfacial reaction of water ice on polycrystalline vanadium and its effects on thermal desorption of water

Thermal desorption and decomposition of water ice deposited onto a polycrystalline V surface were investigated using temperature-programmed desorption and secondary ion mass spectrometry. The water molecules in multilayer films dissociate preferentially at the interface, whereas water desorption from the surface is depressed considerably. The oxygen atoms (hydrogen molecules) formed at the interface are incorporated into the substrate (released into the gas phase) sequentially at temperatures higher than 140 K. The crystallization kinetics of water multilayers is not influenced by the interfacial reaction, but the water desorption rate is depressed by the interfacial reaction even after crystallization. Consequently, thermal desorption of water from the surface and its reaction at the interface are found to be correlated across thin films. This behavior is explainable as dynamic heterogeneity of water in the deeply supercooled region and premelting of metastable ice Ic, where mobile water molecules play a dominant role in both thermal desorption and the interfacial reaction.

Crystallisation of ice in charged Pt nanochannel

Using molecular dynamics simulations, we examine the crystallisation process of the extended simple point charge model (SPC/E) water confined in a charged Pt nanochannel. The presence of the external electric field enhances the surface layering of water and promotes the super-cooled water to crystallise into Ic ice within tens of nanoseconds. Ic ice is found to nucleate from the interior of the water lamina, and the Pt(111) surfaces do not show a remarkable promotion of Ic ice nucleation. Structural analysis reveals that a two-dimensional hydrogen-bond network is built among the water molecules absorbed on the charged Pt surfaces, which influences the bonding of the molecules between the first and the second layers, and disturbs the formation of tetrahedral structures that match Ic ice, finally resulting in the nucleation-free near the walls. Such arrangements of water molecules remain in the subsequent growth of Ic ice and cause the slowdown of growth velocity while approaching surfaces.

Phase changes of filled ice Ih methane hydrate under low temperature and high pressure

Low-temperature and high-pressure experiments were performed with filled ice Ih structure of methane hydrate under 2.0-77.0 GPa and 30-300 K using diamond anvil cells and a helium-refrigeration cryostat. In situ X-ray diffractometry revealed distinct changes in the compressibility of the axial ratios of the host framework with pressure. Raman spectroscopy showed a split in the C-H vibration modes of the guest methane molecules, which was previously explained by the orientational ordering of the guest molecules. The pressure and temperature conditions at the split of the vibration modes agreed well with those of the compressibility change. The results indicate the following: (i) the orientational ordering of the guest methane molecules from an orientationally disordered state occurred at high pressures and low temperatures; and (ii) this guest ordering led to anisotropic contraction in the host framework. Such guest orientational ordering and subsequent anisotropic contraction of the host framework were similar to that reported previously for filled ice Ic hydrogen hydrate. Since phases with different guest-ordering manners were regarded as different phases, existing regions of the guest disordered-phase and the guest ordered-phase were roughly estimated by the X-ray study. In addition, above the pressure of the guest-ordered phase, another high-pressure phase developed in the low-temperature region. The deuterated-water host samples were also examined, and the influence of isotopic effects on guest ordering and phase transformation was observed.

Ice growth in aviation jet fuel

Experimental studies were performed to gain a better understanding of ice growth in aviation jet fuel at low temperatures. Dissolved water precipitated from fuel to form fine water droplets of diameters typically no more than 5μm as the fuel was cooled. Some water droplets could remain in a metastable supercooled state to temperatures below −30°C. At temperatures below that, supercooled water droplets appeared to freeze to form metastable ice particles. Examples of this type of ice have been reported and may be stacking disordered ice (I) composed of randomly stacked layers of cubic ice (Ic) and hexagonal ice (Ih) sequences. Ice particles, exhibiting Ih polymorph characteristics, were found to nucleate and grow on surfaces at sub-zero temperatures. These hexagonal ice particles were observed to grow at the expense of the metastable ice particles near them. The observed mass transfer of water from metastable ice particles to deposition on the hexagonal ice particles in aviation jet fuel was attributed to the augmented Wegener–Bergeron–Findeisen (WBF) process and the Ostwald ripening process. The two processes supported the growth of hexagonal ice particles until the metastable ice particles near them were completely exhausted.

Reply to Bogdan et al.: “Cubic ice” in cirrus clouds under dry and wet conditions

Bogdan et al. (1) discuss the relevance of surface roughness of vapor-deposited so-called “ice Ic” discovered in ref. 2 for ice crystals formed at low temperatures in cirrus clouds. The authors emphasize that for ice nucleation from solute aerosol droplets, the initial ice crystal is coated by residual freeze-concentrated solutions, and they provide images from laboratory freezing experiments on large H2SO4 and NH4-sulfate solution droplets.

Solution coating around ice particles of incipient cirrus clouds

Kuhs et al. (1) report on the nanometer-scale roughness on the surface of laboratory vapor-deposited cubic ice, Ic, and state that such roughness on the surface of cirrus Ic ice particles can influence the surface reactivity, radiative properties, and water vapor uptake coefficient of incipient cirrus clouds. This assumes that the ice surface of cirrus particles is exposed to air. However, this is not the case when cirrus particles are formed by freezing aqueous aerosol drops. Freezing of aqueous drops with ∼20–40 wt% of solute is the mechanism discussed in literature studies mentioned by Kuhs et al., i.e., their refs. 20, 55, 58, and 59.

ChemInform Abstract: Low‐Pressure Synthesis and Characterization of Hydrogen‐Filled Ice Ic.

AbstractAn ice Ic framework partially filled with H2 (H2:H2O‐Ic) is obtained by annealing amorphous ice and hydrogen gas (135—160 K, 8—18 MPa H2).

Topological characterization of crystalline ice structures from coordination sequences

Topological properties of crystalline ice structures are studied by considering ring statistics, coordination sequences, and topological density of different ice phases. The coordination sequences (number of sites at topological distance k from a reference site) have been obtained by direct enumeration until at least 40 coordination spheres for different ice polymorphs. This allows us to study the asymptotic behavior of the mean number of sites in the k-th shell, Mk, for high values of k: Mk~ak(2), a being a structure-dependent parameter. Small departures from a strict parabolic dependence have been studied by considering first and second differences of the series {Mk} for each structure. The parameter a ranges from 2.00 for ice VI to 4.27 for ice XII, and is used to define a topological density for these solid phases of water. Correlations between such topological density and the actual volume of ice phases are discussed. Ices Ih and Ic are found to depart from the general trend in this correlation due to the large void space in their structures.