Water is the most abundant liquid on earth and also the substance with the largest number of anomalies in its properties. It is a prerequisite for life and as such a most important subject of current research in chemical physics and physical chemistry. In spite of its simplicity as a liquid, it has an enormously rich phase diagram where different types of ices, amorphous phases, and anomalies disclose a path that points to unique thermodynamics of its supercooled liquid state that still hides many unraveled secrets. In this review we describe the behavior of water in the regime from ambient conditions to the deeply supercooled region. The review describes simulations and experiments on this anomalous liquid. Several scenarios have been proposed to explain the anomalous properties that become strongly enhanced in the supercooled region. Among those, the second critical-point scenario has been investigated extensively, and at present most experimental evidence point to this scenario. Starting from very low ...

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Water: A Tale of Two Liquids

Resonant ion-dip infrared spectroscopy has been used to record size-specific infrared spectra of C(6)H(6)-(H(2)O)n clusters with n = 1 through 7 in the O-H stretch region. The O-H stretch spectra show a dramatic dependence on cluster size. For the n = 3 to 5 clusters, the transitions can be divided into three types-attributable to free, pi hydrogen-bonded, and single donor water-water O-H stretches-consistent with a C(6)H(6)-(H(2)O)n structure in which benzene is on the surface of a cyclic (H(2)O)n cluster. In n = 6 and 7 clusters, the spectra show distinct new transitions in the 3500 to 3600 wave number region. After comparison of these results with the predictions of ab initio calculations on (H(2)O)n clusters, these new transitions have been assigned to double donor O-H stretches associated with the formation of a more compact, noncyclic structure beginning with (H(2)O)(6). This is the same size cluster for which ab initio calculations predict that a changeover to noncyclic (H(2)O)n structures will occur.

https://science.sciencemag.org/content/sci/265/5168/75.full.pdf

Size-Specific Infrared Spectra of Benzene-(H2O)n Clusters (n = 1 through 7): Evidence for Noncyclic (H2O)n Structures

Selected area electron diffraction is used to monitor structural changes of vapor-deposited water ice in vacuum during warm-up from 15 to 188 K. A progression of three amorphous forms of water ice is found with well-defined transitions. The formation of a high-density amorphous form (Iah) at 15 K is confirmed, and the transition to the more familiar low-density form (Ial) occurs gradually over the range 38 to 68 K. At 131 K, the ice transforms into a third amorphous form (Iar), which precedes the crystallization of cubic ice (Ic) and coexists metastably with Ic from 148 K until at least 188 K. These structural transformations of amorphous water ice can be used to explain hitherto anomalous properties of astrophysical ices. The structural transition from Iah to Ial is responsible for the diffusion and recombination of radicals in ultraviolet-photolyzed interstellar ices at low temperatures. The occurrence and persistence of Iar explains anomalous gas retention and gas release from water-rich ices at temperatures above 150 K.

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Structural transitions in amorphous water ice and astrophysical implications.

Transmission spectra were measured between 1.0 and 2.7 μm for monocrystalline samples of hexagonal water ice at temperatures between 20 and 270 K. Samples were crystallized from liquid water within closed cells, with thicknesses ranging from 100 μm to 1.0 cm. The absorption spectrum of ice changes with temperature in several ways. With higher temperature, the shapes of absorption bands become more smoothed, the strengths of some absorption bands decrease, the absorption in continuum wavelengths increases, and the band centers of some absorption bands shift to shorter wavelengths. In this paper we present the new absorption coefficient spectra along with an examination of the different temperature effects. These data should prove extremely valuable for analysis of near-infrared reflectance spectra of low-temperature icy surfaces, such as those of outer solar system satellites, Kuiper Belt objects, Pluto and Charon, comet nuclei, the polar caps of Mars, and terrestrial snow-and ice-covered regions. The data may also be of value in simulating radiative transfer in clouds of ice particles in the atmospheres of planets.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98JE00738

The temperature‐dependent near‐infrared absorption spectrum of hexagonal H2O ice

Absorption spectra from 4000 to 1200 cm −1 of amorphous solid water and polycrystalline ice I c have been measured between 10 K and 140 K. Warm up and recooling of an H 2 O sample prepared at 10 K gives rise to both irreversible and reversible changes in the peak frequency, band width, and peak height as well as the integrated intensity of the OH stretching band. These spectral effects are related to structural differences. The structure of amorphous solid water also depends on deposition conditions. The optical constants of amorphous so water are determined at 10 K and 80 K from a Kramers-Kronig analysis of the transmission spectra taking into account reflection and interference losses. The astrophysical implication of the temperature dependence of peak frequency and band width of the 3250 cm −1 band in amorphous solid water is discussed briefly.

The infrared spectra of amorphous solid water and ice Ic between 10 and 140 K

Extensive experimental studies of the OH stretching region of the Raman spectra of polycrystalline ice Ih and low density amorphous solid water (H2O (as)) are reported. Analysis of these spectra, using insights from theoretical calculations, leads to the following conclusions: (i) The overall span and distribution of features in the spectra result from strong intermolecular coupling of OH oscillators. This coupling is so strong that the solids cannot be considered to be composed of weakly perturbed water molecules, and the identification of features of their spectra with molecular vibrations is not useful. (ii) At the low end of the OH stretching region there is a totally symmetric mode—that is the amplitudes of motion on all oscillators are in phase, but these amplitudes vary erratically from site to site in the solid. The temperature dependence of the shift in frequency of this mode is likely all accounted for by thermal expansion, the temperature dependence of its FWHM is accurately described as due to scattering by optical phonons with effective frequency 200 cm−1. (iii) The earlier proposed interpretation of the Raman spectrum of H2O(as) by Venkatesh, Bates and Rice [J. Chem. Phys. 63, 1065 (1975)] is withdrawn. Their interpetation was based on the assumptions that they had observed the spectrum of high density H2O (as), which we now believe to be incorrect, and that the solid could be considered an assembly of weakly perturbed water molecules, which we now believe to be untenable.

Raman spectroscopic studies of the OH stretching region of low density amorphous solid water and of polycrystalline ice Ih

The 2500–4000 cm−1 Raman and infrared spectra of low density amorphous solid water and of polycrystalline ice I

The primary goal of this work is to evaluate how BN and WC particles affect the mechanical properties and damage development behaviours of aluminum alloy-2048. Heat treatments for composites are also being investigated to improve mechanical properties. Tensile experiments reveal that BN particle reinforcement outperforms WC reinforcement in strength and flexibility for composites. T4 treatment, rather than traditional peak-aging treatment, is recommended for the composites (T6). The particle size distribution in 10v% WC/Al-2048 is the best in the three composites with the largest size of 16 µm and 80% of particles are from 6 to 10 µm. Tensile tests illustrate that 15v% BN/Al-2048 composite demonstrates a 9 and 14% rise in its ultimate tensile stress and 28 and 120% increases in its elongation. T4 heat treatment with an additional 0.6 percent prestrain can produce composites with the same UTS and 0.2 percent proof stress as T6 treatment, but the ultimate elongation below T4 treatment is over 100 percent more than that under T6 treatment. To make sense of the test results, an observation of the damage evolution behaviors of the reinforcing particles provides a concept that the composites’ strength is primarily determined by the balance between the reinforcing particles sharing the load and creating strain discontinuity in the matrix. The fraction of broken particles in the 20v% WC/Al-2048 composite as a function of strain is much higher than that in the 15v% BN/Al-2048 composite. Because of their tolerance for substantial strain at the interface, maximum K1c, and moderate thermal extension, BN elements can share a lot of loads and provide more excellent reinforcement than WC particles in terms of composite strength and flexibility.

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T. C. Sivakumar

Papers

Raman spectroscopic studies of the OH stretching region of low density amorphous solid water and of polycrystalline ice Ih

The 2500–4000 cm−1 Raman and infrared spectra of low density amorphous solid water and of polycrystalline ice I

Impact of BN and WC Particulate Reinforcements on Mechanical Properties and Damage Development of Al-2048 Metal Matrix Composites