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Ice XIX
Ice XIX is a proposed crystalline phase of water. Along with ice XV, it is one of two phases of ice directly related to ice VI. Ice XIX is prepared by cooling HCl-doped ice VI at a pressure above 1.6 GPa down to about 100 K. As of 2022, its crystal structure has not been elucidated. Discovery Initial report The first report regarding ice XIX was published in 2018 by Thomas Loering's group from Austria. They quenched HCl-doped ice VI to 77 K at different pressures between 1.0 and 1.8 GPa to collect differential scanning calorimetry (DSC) thermograms, dielectric spectrum, Raman spectrum, and X-ray diffraction patterns. In the DSC signals, there was an endothermic feature at about 110 K in addition to the endotherm corresponding to ice XV-VI transition. Additionally, the Raman spectra, dielectric properties, and the ratio of the lattice parameters differed from those of ice XV. Based on these observations, they proposed the existence of a second hydrogen-ordered phase of i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice XV
Ice XV is a crystalline form of ice, the proton-ordered form of ice VI. It is created by cooling hydrochloric-acid-doped water to around 130 K at 1 GPa (9820 atm). Ordinary water ice is known as ice Ih, (in the Bridgman nomenclature). Different types of ice, from ice II to ice XVI, have been created in the laboratory at different temperatures and pressures. On 14 June 2009, Christoph Salzmann at the University of Oxford and colleagues reported having created ice XV and say that its properties differ significantly from those predicted. In particular, ice XV is antiferroelectric rather than ferroelectric Ferroelectricity is a characteristic of certain materials that have a spontaneous electric polarization that can be reversed by the application of an external electric field. All ferroelectrics are also piezoelectric and pyroelectric, with the ad ... as had been predicted. References * Water ice {{inorganic-compound-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice VI
Ice VI is a form of ice that exists at high pressure at the order of about 1 GPa (= 10 000 bar) and temperatures ranging from 130 up to 355 Kelvin (−143 °C up to 82 °C); see also the phase diagram of water. Its discovery and the discovery of other high-pressure forms of water were published by P.W. Bridgman in January 1912. It is part of one of the inner layers of Titan. Properties Ice VI has a density of 1.31 g/cm3 and a tetragonal crystal system with the space group P42/nmc; its unit cell contains 10 water molecules and has the dimensions a=6.27 Å and c=5.79 Å. The triple point of ''ice VI'' with ice VII and liquid water is at about 82 °C and 2.22 GPa and its triple point with ice V and liquid water is at 0.16 °C and 0.6324 GPa = 6324 bar. www1.lsbu.ac.uk, version of 9 September ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Differential Scanning Calorimetry
Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. The technique was developed by E. S. Watson and M. J. O'Neill in 1962, and introduced commercially at the 1963 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. The first adiabatic differential scanning calorimeter that could be used in biochemistry was developed by P. L. Privalov and D. R. Monaselidze in 1964 at Institute of Physics in Tbilisi, Georgia. The term DSC was coined to descr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dielectric Spectroscopy
Dielectric spectroscopy (which falls in a subcategory of impedance spectroscopy) measures the dielectric properties of a medium as a function of frequency.Kremer F., Schonhals A., Luck W. Broadband Dielectric Spectroscopy. – Springer-Verlag, 2002. It is based on the interaction of an external field with the electric dipole moment of the sample, often expressed by permittivity. It is also an experimental method of characterizing electrochemical systems. This technique measures the impedance of a system over a range of frequencies, and therefore the frequency response of the system, including the energy storage and dissipation properties, is revealed. Often, data obtained by electrochemical impedance spectroscopy (EIS) is expressed graphically in a Bode plot or a Nyquist plot. Impedance is the opposition to the flow of alternating current (AC) in a complex system. A passive complex electrical system comprises both energy dissipater (resistor) and energy storage (capacitor) elem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Raman Spectroscopy
Raman spectroscopy () (named after Indian physicist C. V. Raman) is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. A source of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range is used, although X-rays can also be used. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy typically yields similar yet complementary information. Typically, a sample is illuminated with a laser beam. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
X-ray Diffraction
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles and intensities of these diffracted beams, a crystallographer can produce a three-dimensional picture of the density of electrons within the crystal. From this electron density, the mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their crystallographic disorder, and various other information. Since many materials can form crystals—such as salts, metals, minerals, semiconductors, as well as various inorganic, organic, and biological molecules—X-ray crystallography has been fundamental in the development of many scientific fields. In its first decades of use, this method determined the size of atoms, the lengths and types of chemical bonds, and the atomic-scale differences among variou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deuterium
Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutrons in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom of deuterium among all atoms of hydrogen (see heavy water). Thus deuterium accounts for approximately 0.0156% by number (0.0312% by mass) of all the naturally occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see Vienna Standard Mean Ocean Water). ( Tritium is yet another hydrogen isotope, with two neutrons, that is far more rare and is radioactive.) The name ''deuterium'' is derived from the Greek , meaning "second", to denote the two particles composing the nucleus. De ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rietveld Refinement
Rietveld refinement is a technique described by Hugo Rietveld for use in the characterisation of crystalline materials. The neutron and X-ray diffraction of powder samples results in a pattern characterised by reflections (peaks in intensity) at certain positions. The height, width and position of these reflections can be used to determine many aspects of the material's structure. The Rietveld method uses a least squares approach to refine a theoretical line profile until it matches the measured profile. The introduction of this technique was a significant step forward in the diffraction analysis of powder samples as, unlike other techniques at that time, it was able to deal reliably with strongly overlapping reflections. The method was first implemented in 1967, and reported in 1969 for the diffraction of monochromatic neutrons where the reflection-position is reported in terms of the Bragg angle, 2''θ''. This terminology will be used here although the technique is equally appl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clausius–Clapeyron Relation
The Clausius–Clapeyron relation, named after Rudolf Clausius and Benoît Paul Émile Clapeyron, specifies the temperature dependence of pressure, most importantly vapor pressure, at a discontinuous phase transition between two phases of matter of a single constituent. Its relevance to meteorology and climatology is the increase of the water-holding capacity of the atmosphere by about 7% for every 1 °C (1.8 °F) rise in temperature. Definition On a pressure–temperature (''P''–''T'') diagram, the line separating the two phases is known as the coexistence curve. The Clapeyron relation gives the slope of the tangents to this curve. Mathematically, :\frac = \frac=\frac, where \mathrmP/\mathrmT is the slope of the tangent to the coexistence curve at any point, L is the specific latent heat, T is the temperature, \Delta v is the specific volume change of the phase transition, and \Delta s is the specific entropy change of the phase transition. The Clausius–Cla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
