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In condensed matter physics and materials science, an amorphous solid is a solid that lacks the long-range order that is characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymously with amorphous solid; however, these terms refer specifically to amorphous materials that undergo a glass transition. Examples of amorphous solids include glasses, metallic glasses, and certain types of plastics and polymers.
In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. If the ball is only slightly pushed, it will settle back into its hollow, but a stronger push may start the ball rolling down the slope. Bowling pins show similar metastability by either merely wobbling for a moment or tipping over completely. A common example of metastability in science is isomerisation. Higher energy isomers are long lived because they are prevented from rearranging to their preferred ground state by barriers in the potential energy.
Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which increases the substance's temperature to the melting point. At the melting point, the ordering of ions or molecules in the solid breaks down to a less ordered state, and the solid melts to become a liquid.
In chemistry, thermodynamics, and other related fields, a phase transition is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states of matter: solid, liquid, and gas, and in rare cases, plasma. A phase of a thermodynamic system and the states of matter have uniform physical properties. During a phase transition of a given medium, certain properties of the medium change as a result of the change of external conditions, such as temperature or pressure. This can be a discontinuous change; for example, a liquid may become gas upon heating to its boiling point, resulting in an abrupt change in volume. The identification of the external conditions at which a transformation occurs defines the phase transition point.
Vitrification is the full or partial transformation of a substance into a glass, that is to say, a non-crystalline amorphous solid. Glasses differ from liquids structurally and glasses possess a higher degree of connectivity with the same Hausdorff dimensionality of bonds as crystals: dimH = 3. In the production of ceramics, vitrification is responsible for their impermeability to water.
An amorphous metal is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystalline in their solid state, which means they have a highly ordered arrangement of atoms. Amorphous metals are non-crystalline, and have a glass-like structure. But unlike common glasses, such as window glass, which are typically electrical insulators, amorphous metals have good electrical conductivity and can show metallic luster.
The molar heat capacity of a chemical substance is the amount of energy that must be added, in the form of heat, to one mole of the substance in order to cause an increase of one unit in its temperature. Alternatively, it is the heat capacity of a sample of the substance divided by the amount of substance of the sample; or also the specific heat capacity of the substance times its molar mass. The SI unit of molar heat capacity is joule per kelvin per mole, J⋅K−1⋅mol−1.
Boron trioxide or diboron trioxide is the oxide of boron with the formula B2O3. It is a colorless transparent solid, almost always glassy (amorphous), which can be crystallized only with great difficulty. It is also called boric oxide or boria. It has many important industrial applications, chiefly in ceramics as a flux for glazes and enamels and in the production of glasses.
Amorphous ice is an amorphous solid form of water. Common ice is a crystalline material wherein the molecules are regularly arranged in a hexagonal lattice, whereas amorphous ice lacks long-range order in its molecular arrangement. Amorphous ice is produced either by rapid cooling of liquid water, or by compressing ordinary ice at low temperatures.
Polyamorphism is the ability of a substance to exist in several different amorphous modifications. It is analogous to the polymorphism of crystalline materials. Many amorphous substances can exist with different amorphous characteristics. However, polyamorphism requires two distinct amorphous states with a clear, discontinuous (first-order) phase transition between them. When such a transition occurs between two stable liquid states, a polyamorphic transition may also be referred to as a liquid–liquid phase transition.
Rydberg matter is an exotic phase of matter formed by Rydberg atoms; it was predicted around 1980 by É. A. Manykin, M. I. Ozhovan and P. P. Poluéktov. It has been formed from various elements like caesium, potassium, hydrogen and nitrogen; studies have been conducted on theoretical possibilities like sodium, beryllium, magnesium and calcium. It has been suggested to be a material that diffuse interstellar bands may arise from. Circular Rydberg states, where the outermost electron is found in a planar circular orbit, are the most long-lived, with lifetimes of up to several hours, and are the most common.
The glass–liquid transition, or glass transition, is the gradual and reversible transition in amorphous materials from a hard and relatively brittle "glassy" state into a viscous or rubbery state as the temperature is increased. An amorphous solid that exhibits a glass transition is called a glass. The reverse transition, achieved by supercooling a viscous liquid into the glass state, is called vitrification.
Johari–Goldstein relaxation, also known as the JG β-relaxation, is a universal property of glasses and certain other disordered materials. Proposed in 1969 by Martin Goldstein, JG β-relaxation were described as a secondary relaxation mechanism required to explain the viscosity behavior of liquids approaching the glass transition in the potential energy landscape picture presented in Goldstein's seminal 1969 paper. Previous experiments on glass forming liquids showed multiple relaxation times present in liquids measured by time dependent compliance measurements. Gyan Johari and Martin Goldstein measured the dielectric loss spectrum of a set of rigid glass forming molecules to further test the hypothesis of Goldstein in 1969. The relaxation, a peak in mechanical or dielectric loss at a particular frequency, had previously been attributed to a type of molecular flexibility. The fact that such a loss peak shows up in glasses of rigid molecules lacking this flexibility demonstrated its universal character.
In condensed matter physics and physical chemistry, the terms viscous liquid, supercooled liquid, and glass forming liquid are often used interchangeably to designate liquids that are at the same time highly viscous, can be or are supercooled, and able to form a glass.
Charles Austen Angell was a renowned Australian and American physical chemist known for his prolific and highly cited research on the chemistry and physics of glasses and glass-forming liquids. He was internationally recognized as a luminary in the fields of glasses, liquids, water and ionic liquids.
The structure of liquids, glasses and other non-crystalline solids is characterized by the absence of long-range order which defines crystalline materials. Liquids and amorphous solids do, however, possess a rich and varied array of short to medium range order, which originates from chemical bonding and related interactions. Metallic glasses, for example, are typically well described by the dense random packing of hard spheres, whereas covalent systems, such as silicate glasses, have sparsely packed, strongly bound, tetrahedral network structures. These very different structures result in materials with very different physical properties and applications.
In glass physics, fragility characterizes how rapidly the dynamics of a material slows down as it is cooled toward the glass transition: materials with a higher fragility have a relatively narrow glass transition temperature range, while those with low fragility have a relatively broad glass transition temperature range. Physically, fragility may be related to the presence of dynamical heterogeneity in glasses, as well as to the breakdown of the usual Stokes–Einstein relationship between viscosity and diffusion. Fragility has no direct relationship with the colloquial meaning of the word "fragility", which more closely relates to the brittleness of a material.
Paul Francis McMillan was a British chemist who held the Sir William Ramsay Chair of Chemistry at University College London. His research considered the study of matter under extreme conditions of temperature and pressure, with a focus on phase transitions, amorphisation, and the study of glassy states. He has also investigated the survival of bacteria and larger organisms (tardigrades) under extreme compression, studies of amyloid fibrils, the synthesis and characterisation of carbonitride nanocrystals and the study of water motion in confined environments. He has made extensive use of Raman spectroscopy together with X-ray diffraction and neutron scattering techniques.
Matthieu Wyart is a French physicist. He is a professor of physics at EPFL and the head of the Physics of Complex Systems Laboratory.
References
- ↑ Angell CA, Rao KJ (July 1, 1972). "Configurational Excitations in Condensed Matter, and the Bond Lattice Model for the Liquid-Glass Transition" . The Journal of Chemical Physics . 57 (1): 470–481. Bibcode:1972JChPh..57..470A. doi:10.1063/1.1677987.
- ↑ Ojovan MI (September 24, 2008). "Configurons: Thermodynamic Parameters and Symmetry Changes at Glass Transition". Entropy . 10 (3): 334–364. Bibcode:2008Entrp..10..334O. doi: 10.3390/e10030334 .
- ↑ Salmon, Philip S. (October 1, 2002). "Order within disorder" . Nature Materials . 1 (2): 87–88. doi:10.1038/nmat737. ISSN 1476-4660. PMID 12618817. S2CID 39062607.
- ↑ Medvedev NN, Geiger A, Brostow W (1990-12-01). "Distinguishing liquids from amorphous solids: Percolation analysis on the Voronoi network" . The Journal of Chemical Physics . 93 (11): 8337–8342. Bibcode:1990JChPh..93.8337M. doi:10.1063/1.459711.
- ↑ Ojovan MI (29 March 2021). "The Modified Random Network (MRN) Model within the Configuron Percolation Theory (CPT) of Glass Transition". Ceramics . 4 (2): 121–134. doi: 10.3390/ceramics4020011 . hdl: 10044/1/88828 .
- ↑ Quinn LY, Krishnaswamy R, Quinn TR (December 16, 1980). "Configuron dependence on translation of specific condon pairs. I. Helical regions of human alpha and beta globins" . Biochemical and Biophysical Research Communications . 97 (3): 868–874. doi:10.1016/0006-291X(80)91457-6. PMID 7470154.