In condensed matter physics and materials science, an amorphous (from the Greek a, without, morphé, shape, form) or non-crystalline solid is a solid that lacks the long-range order that is characteristic of a crystal. In some older books, the term has been used synonymously with glass. Nowadays, "glassy solid" or "amorphous solid" is considered to be the overarching concept, and glass the more special case: Glass is an amorphous solid that exhibits a glass transition. Polymers are often amorphous. Other types of amorphous solids include gels, thin films, and nanostructured materials such as glass doors and windows.
Amorphous materials have an internal structure made of interconnected structural blocks. These blocks can be similar to the basic structural units found in the corresponding crystalline phase of the same compound. Whether a material is liquid or solid depends primarily on the connectivity between its elementary building blocks so that solids are characterized by a high degree of connectivity whereas structural blocks in fluids have lower connectivity.
In pharmaceutical industry, the amorphous drugs were shown to have higher bioavailability than their crystalline counterparts due to the high solubility of amorphous phase. Moreover, certain compounds can undergo precipitation in their amorphous form in vivo, and they can decrease each other's bioavailability if administered together.
Even amorphous materials have some shortrange order at the atomic length scale due to the nature of chemical bonding (see structure of liquids and glasses for more information on non-crystalline material structure). Furthermore, in very small crystals a large fraction of the atoms are the crystal; relaxation of the surface and interfacial effects distort the atomic positions, decreasing the structural order. Even the most advanced structural characterization techniques, such as x-ray diffraction and transmission electron microscopy, have difficulty in distinguishing between amorphous and crystalline structures on these length scales.
Amorphous phases are important constituents of thin films, which are solid layers of a few nanometres to some tens of micrometres thickness deposited upon a substrate. So-called structure zone models were developed to describe the micro structure and ceramics of thin films as a function of the homologous temperature Th that is the ratio of deposition temperature over melting temperature. According to these models, a necessary (but not sufficient) condition for the occurrence of amorphous phases is that Th has to be smaller than 0.3, that is the deposition temperature must be below 30% of the melting temperature. For higher values, the surface diffusion of deposited atomic species would allow for the formation of crystallites with long range atomic order.
Regarding their applications, amorphous metallic layers played an important role in the discussion of a suspected superconductivity in amorphous metals. Today, optical coatings made from TiO2, SiO2, Ta2O5 etc. and combinations of them in most cases consist of amorphous phases of these compounds. Much research is carried out into thin amorphous films as a gas separating membrane layer. The technologically most important thin amorphous film is probably represented by few nm thin SiO2 layers serving as isolator above the conducting channel of a metal-oxide semiconductor field-effect transistor (MOSFET). Also, hydrogenated amorphous silicon, a-Si:H in short, is of technical significance for thin-film solar cells. In case of a-Si:H the missing long-range order between silicon atoms is partly induced by the presence by hydrogen in the percent range.
The occurrence of amorphous phases turned out as a phenomenon of particular interest for studying thin-film growth. Remarkably, the growth of polycrystalline films is often used and preceded by an initial amorphous layer, the thickness of which may amount to only a few nm. The most investigated example is represented by thin multicrystalline silicon films, where such as the unoriented molecule. An initial amorphous layer was observed in many studies. Wedge-shaped polycrystals were identified by transmission electron microscopy to grow out of the amorphous phase only after the latter has exceeded a certain thickness, the precise value of which depends on deposition temperature, background pressure and various other process parameters. The phenomenon has been interpreted in the framework of Ostwald's rule of stages that predicts the formation of phases to proceed with increasing condensation time towards increasing stability. Experimental studies of the phenomenon require a clearly defined state of the substrate surface and its contaminant density etc., upon which the thin film is deposited.
Amorphous carbonia, also called a-carbonia or a-CO2, is an exotic amorphous solid form of carbon dioxide that is analogous to amorphous silica glass. It was first made in the laboratory in 2006 by subjecting dry ice to high pressures (40-48 gigapascal, or 400,000 to 480,000 atmospheres), in a diamond anvil cell. Amorphous carbonia is not stable at ordinary pressures—it quickly reverts to normal CO2.While normally carbon dioxide forms molecular crystals, where individual molecules are bound by Van der Waals forces, in amorphous carbonia a covalently bound three-dimensional network of atoms is formed, in a structure analogous to silicon dioxide or germanium dioxide glass.
Mixtures of a-carbonia and a-silica may be a prospective very hard and stiff glass material stable at room temperature. Such glass may serve as protective coatings, e.g. in microelectronics.
The discovery has implications for astrophysics, as interiors of massive planets may contain amorphous solid carbon dioxide.Amorphous ice
Amorphous ice (non-crystalline ("vitreous") ice) is an amorphous solid form of water. Common ice is a crystalline material where the molecules are regularly arranged in a hexagonal lattice whereas amorphous ice is distinguished by a lack of long-range order in its molecular arrangement. Amorphous ice is produced either by rapid cooling of liquid water (so the molecules do not have enough time to form a crystal lattice) or by compressing ordinary ice at low temperatures.
Although almost all water ice on Earth is the familiar crystalline ice Ih, amorphous ice dominates in the depths of interstellar medium, making this likely the most common structure for H2O in the universe at large.Just as there are many different crystalline forms of ice (currently 17+ known), there are also different forms of amorphous ice, distinguished principally by their densities.Beryllium oxide
Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO. This colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of most metals. As an amorphous solid, beryllium oxide is white. Its high melting point leads to its use as a refractory material. It occurs in nature as the mineral bromellite. Historically and in materials science, beryllium oxide was called glucina or glucinium oxide. Formation of BeO from beryllium and oxygen releases the highest energy per mass of reactants for any chemical reaction, close to 24 MJ/kg.Charantoside
Charantoside is any of several related cucurbitane triterpenoid glycosides found in the fruits bitter melon vine (Momordica charantia). They include:
charantoside I, (19R,23E)-5β,19-Epoxy-19-methoxycucurbita-6,23,25-trien-3β-ol 3-O-β-D-glucopyranoside: amorphous solid.
charantoside II, (19R,23R)-5β,19-Epoxy-19,23-dimethoxycucurbita-6,24-dien-3β-ol 3-O-β-D-allopyranoside: amorphous solid.
charantoside III, (23E)-5β,19-Epoxycucurbita-6,23,25-trien-3β-ol 3-O-β-D-glucopyranoside: amorphous solid.
charantoside IV, (23E)-5β,19-Epoxycucurbita-6,23,25-trien-3β-ol 3-O-β-D-allopyranoside: colorless needles, melting at 256–260 °C.
charantoside V, (23R)-5β,19-Epoxy-23-methoxycucurbita-6,24-dien-3β-ol 3-O-β-D-glucopyranoside: colorless needles, melting at 235–240 °C.
charantoside VI, (23S)-5β,19-Epoxy-23-methoxycucurbita-6,24-dien-3β-ol 3-O-β-D-allopyranoside: amorphous solid.
charantoside VII, (23E)-3β-Hydroxycucurbita-6,23,25-trien-5β,19-olide 3-O-β-Dglucopyranoside: colorless needles, melting at 258–262 °C
charantoside VIII, (23E)-3β-Hydroxy-7β,25-dimethoxycucurbita-5,23-dien-19-al 3-O-β-D-glucopyranoside: amorphous solid.Charantosides I through VIII can be extracted from the fresh fruit with methanol and ethyl acetate.Crystallite
A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. The orientation of crystallites can be random with no preferred direction, called random texture, or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter. Crystallites are also referred to as grains. The areas where crystallites meet are known as grain boundaries. Polycrystalline or multicrystalline materials, or polycrystals are solids that are composed of many crystallites of varying size and orientation.
Most inorganic solids are polycrystalline, including all common metals, many ceramics, rocks, and ice. The extent to which a solid is crystalline (crystallinity) has important effects on its physical properties. Sulfur, while usually polycrystalline, may also occur in other allotropic forms with completely different properties. Although crystallites are referred to as grains, powder grains are different, as they can be composed of smaller polycrystalline grains themselves.While the structure of a (monocrystalline) crystal is highly ordered and its lattice is continuous and unbroken, amorphous materials, such as glass and many polymers, are non-crystalline and do not display any structures as their constituents are not arranged in an ordered manner. Polycrystalline structures and paracrystalline phases are in between these two extremes.Differential scanning calorimetry
Differential scanning calorimetry, or 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 describe this instrument, which measures energy directly and allows precise measurements of heat capacity.Types of DSC:
Power-compensated DSC, keeps power supply constant
Heat-flux DSC, keeps heat flux constantHelium-4
Helium-4 (42He or 4He) is a non-radioactive isotope of the element helium. It is by far the most abundant of the two naturally occurring isotopes of helium, making up about 99.99986% of the helium on Earth. Its nucleus is identical to an alpha particle, and consists of two protons and two neutrons.
Alpha decay of heavy elements in the Earth's crust is the source of most naturally occurring helium-4 on Earth. While it is also produced by nuclear fusion in stars, most helium-4 in the Sun and in the universe is thought to have been produced by the Big Bang, and is referred to as "primordial helium". However, primordial helium-4 is largely absent from the Earth, having escaped during the high-temperature phase of Earth's formation. Radioactive decay from other elements is the source of most of the helium-4 found on Earth, produced after the planet cooled and solidified.
Helium-4 makes up about one quarter of the ordinary matter in the universe by mass, with almost all of the rest being hydrogen.
When liquid helium-4 is cooled to below 2.17 kelvins (–271.17 °C), it becomes a superfluid, with properties that are very unlike those of an ordinary liquid. For example, if superfluid helium-4 is kept in an open vessel, a thin film will climb up the sides of the vessel and overflow. In this state and situation, it is called a "Rollin film". This strange behavior is a result of the Clausius–Clapeyron relation and cannot be explained by the current model of classical mechanics, nor by nuclear or electrical models – it can only be understood as a quantum-mechanical phenomenon. The total spin of the helium-4 nucleus is an integer (zero), and therefore it is a boson (as are neutral atoms of helium-4). The superfluid behavior is now understood to be a manifestation of Bose–Einstein condensation, which occurs only with collections of bosons.
It is theorized that, at 0.2 K and 50 atm, solid helium-4 may be a superglass (an amorphous solid exhibiting superfluidity).
Helium-4 also exists on the Moon and—as on Earth—it is the most abundant helium isotope.Iridium tetrachloride
Iridium tetrachloride is an inorganic compound with the approximate formula IrCl4(H2O)n. It is a water-soluble dark brown amorphous solid. A well defined derivative is ammonium hexachloroiridate ((NH4)2IrCl6). It is used to prepare catalysts, such as the Henbest Catalyst for transfer hydrogenation of cyclohexanones.Lamellar structure
Lamellar structures or microstructures are composed of fine, alternating layers of different materials in the form of lamellae. They are often observed in cases where a phase transformation front moves quickly, leaving behind two solid products, as in rapid cooling of eutectic (such as solder) or eutectoid (such as pearlite) systems.
Such conditions force phases of different composition to form but allow little time for diffusion to produce those phases' equilibrium compositions. Fine lamellae solve this problem by shortening the diffusion distance between phases, but their high surface energy makes them unstable and prone to break up when annealing allows diffusion to progress. A deeper eutectic or more rapid cooling will result in finer lamellae; as the size of an individual lamellum approaches zero, the system will instead retain its high-temperature structure. Two common cases of this include cooling a liquid to form an amorphous solid, and cooling eutectoid austenite to form martensite.
In biology, normal adult bones possess a lamellar structure which may be disrupted by some diseases.Network covalent bonding
A network solid or covalent network solid is a chemical compound (or element) in which the atoms are bonded by covalent bonds in a continuous network extending throughout the material. In a network solid there are no individual molecules, and the entire crystal or amorphous solid may be considered a macromolecule. Formulas for network solids, like those for ionic compounds, are simple ratios of the component atoms represented by a formula unit.Examples of network solids include diamond with a continuous network of carbon atoms and silicon dioxide or quartz with a continuous three-dimensional network of SiO2 units. Graphite and the mica group of silicate minerals structurally consist of continuous two-dimensional sheets covalently bonded within the layer, with other bond types holding the layers together. Disordered network solids are termed glasses. These are typically formed on rapid cooling of melts so that little time is left for atomic ordering to occur.Paracrystalline
Paracrystalline materials are defined as having short- and medium-range ordering in their lattice (similar to the liquid crystal phases) but lacking crystal-like long-range ordering at least in one direction.
Ordering is the regularity in which atoms appear in a predictable lattice, as measured from one point. In a highly ordered, perfectly crystalline material, or single crystal, the location of every atom in the structure can be described exactly measuring out from a single origin. Conversely, in a disordered structure such as a liquid or amorphous solid, the location of the nearest and, perhaps, second-nearest neighbors can be described from an origin (with some degree of uncertainty) and the ability to predict locations decreases rapidly from there out. The distance at which atom locations can be predicted is referred to as the correlation length . A paracrystalline material exhibits correlation somewhere between the fully amorphous and fully crystalline.
The primary, most accessible source of crystallinity information is X-ray diffraction and cryo-electron microscopy, although other techniques may be needed to observe the complex structure of paracrystalline materials, such as fluctuation electron microscopy in combination with density of states modeling of electronic and vibrational states. Scanning transmission electron microscopy can provide real-space and reciprocal space characterization of paracrystallinity in nanoscale material, such as quantum dot solids.
The scattering of X-rays, neutrons and electrons on paracrystals is quantitatively described by the theories of the ideal and real paracrystal.
Rolf Hosemann’s definition of an ideal paracrystal is: "The electron density distribution of any material is equivalent to that of a paracrystal when there is for every building block one ideal point so that the distance statistics to other ideal points is identical for all of these points. The electron configuration of each building block around its ideal point is statistically independent of its counterpart in neighboring building blocks. A building block corresponds then to the material content of a cell of this "blurred" space lattice, which is to be considered a paracrystal."
Numerical differences in analyses of diffraction experiments on the basis of either of these two theories of paracrystallinity can often be neglected.
Just like ideal crystals, ideal paracrystals extend theoretically to infinity. Real paracrystals, on the other hand, follow the empirical α*-law, which restricts their size. That size is also indirectly proportional to the components of the tensor of the paracrystalline distortion. Larger solid state aggregates are then composed of micro-paracrystals.
The words "paracrystallinity" and "paracrystal" were coined by the late Friedrich Rinne in the year 1933. Their German equivalents, e.g. "Parakristall", appeared in print one year earlier.Residual entropy
Residual entropy is the difference in entropy between a non-equilibrium state and crystal state of a substance close to absolute zero. This term is used in condensed matter physics to describe the entropy at zero kelvin of a glass or plastic crystal referred to the crystal state, whose entropy is zero according to the third law of thermodynamics. It occurs if a material can exist in many different states when cooled. The most common non-equilibrium state is vitreous state, glass.
A common example is the case of carbon monoxide, which has a very small dipole moment. As the carbon monoxide crystal is cooled to absolute zero, few of the carbon monoxide molecules have enough time to align themselves into a perfect crystal, (with all of the carbon monoxide molecules oriented in the same direction). Because of this, the crystal is locked into a state with different corresponding microstates, giving a residual entropy of , rather than zero.
Another example is any amorphous solid (glass). These have residual entropy, because the atom-by-atom microscopic structure can be arranged in a huge number of different ways across a macroscopic system.Silicon monosulfide
Silicon monosulfide is a chemical compound of silicon and sulfur. The chemical formula is SiS. Molecular SiS has been detected at high temperature in the gas phase. The gas phase molecule has an Si-S bondlength of 192.93 pm, this compares to the normal single bond length of 216 pm, and is shorter than the Si=S bond length of around 201 pm reported in an organosilanethione. Historically a pale yellow-red amorphous solid compound has been reported. The behavior of silicon can be contrasted with germanium which forms a stable solid monosulfide.Solid
Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). In solids molecules are closely packed. It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a gas does. The atoms in a solid are tightly bound to each other, either in a regular geometric lattice (crystalline solids, which include metals and ordinary ice) or irregularly (an amorphous solid such as common window glass). Solids cannot be compressed with little pressure whereas gases can be compressed with little pressure because in gases molecules are loosely packed.
The branch of physics that deals with solids is called solid-state physics, and is the main branch of condensed matter physics (which also includes liquids). Materials science is primarily concerned with the physical and chemical properties of solids. Solid-state chemistry is especially concerned with the synthesis of novel materials, as well as the science of identification and chemical composition.Spin glass
In condensed matter physics, a spin glass is a disordered magnet, where the magnetic spins of the component atoms (the orientation of the north and south magnetic poles in three-dimensional space) are not aligned in a regular pattern. The term "glass" comes from an analogy between the magnetic disorder in a spin glass and the positional disorder of a conventional, chemical glass, e.g., a window glass. In window glass or any amorphous solid the atomic bond structure is highly irregular; in contrast, a crystal has a uniform pattern of atomic bonds. In ferromagnetic solid, magnetic spins all align in the same direction; this would be analogous to a crystal.
The individual atomic bonds in a spin glass are a mixture of roughly equal numbers of ferromagnetic bonds (where neighbors have the same orientation) and antiferromagnetic bonds (where neighbors have exactly the opposite orientation: north and south poles are flipped 180 degrees). These patterns of aligned and misaligned atomic magnets create what are known as frustrated interactions - distortions in the geometry of atomic bonds compared to what would be seen in a regular, fully aligned solid. They may also create situations where more than one geometric arrangement of atoms is stable.
Spin glasses and the complex internal structures that arise within them are termed "metastable" because they are "stuck" in stable configurations other than the lowest-energy configuration (which would be aligned and ferromagnetic). The mathematical complexity of these structures is difficult but fruitful to study experimentally or in simulations, with applications to artificial neural networks in computer science, in addition to physics, chemistry, and materials science.Strain crystallization
Strain crystallization is a phenomenon in which an initially amorphous solid material undergoes a phase transformation due to the application of strain. Strain crystallization occurs in natural rubber, as well as other elastomers and polymers. The phenomenon has important effects on strength and fatigue properties.Variable-range hopping
Variable-range hopping is a model used to describe carrier transport in a disordered semiconductor of in amorphous solid by hopping in an extended temperature range. It has a characteristic temperature dependence of
where is a parameter dependent on the model under consideration.Vitreous
Vitreous may refer to:
Glass, an amorphous solid material
Materials, such as minerals or ceramics, that have gone through vitrification
Vitreous enamel, a coating on metal, glass or ceramic
Vitreous lustre, a glassy luster or sheen on a mineral surface
Vitreous body, a clear gel that fills the space between the lens and the retina in vertebrate eyes
Vitreous membrane, a layer of collagen separating the vitreous body from the rest of the eyeVitrification
Vitrification (from Latin vitreum, "glass" via French vitrifier) is the transformation of a substance into a glass, that is to say a non-crystalline amorphous solid. In the production of ceramics, vitrification is responsible for its impermeability to water.Vitrification is usually achieved by heating materials until they liquidize, then cooling the liquid, often rapidly, so that it passes through the glass transition to form a vitrified solid. Certain chemical reactions also result in glasses.
In terms of chemistry, vitrification is characteristic for amorphous materials or disordered systems and occurs when bonding between elementary particles (atoms, molecules, forming blocks) becomes higher than a certain threshold value. Thermal fluctuations break the bonds; therefore, the lower the temperature, the higher the degree of connectivity. Because of that, amorphous materials have a characteristic threshold temperature termed glass transition temperature (Tg): below Tg amorphous materials are glassy whereas above Tg they are molten.
The most common applications are in the making of pottery, glass, and some types of food, but there are many others, such as the vitrification of an antifreeze-like liquid in cryopreservation.
In a different sense of the word, the embedding of material inside a glassy matrix is also called vitrification. An important application is the vitrification of radioactive waste to obtain a substance that is hopefully safer and more stable for disposal.