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36-451: Indium phosphide can be prepared from the reaction of white phosphorus and indium iodide at 400 °C., also by direct combination of the purified elements at high temperature and pressure, or by thermal decomposition of a mixture of a trialkyl indium compound and phosphine . The application fields of InP splits up into three main areas. It is used as the basis for optoelectronic components, high-speed electronics, and photovoltaics InP

72-411: A fully stable digital state. Metastability in the brain is a phenomenon studied in computational neuroscience to elucidate how the human brain recognizes patterns. Here, the term metastability is used rather loosely. There is no lower-energy state, but there are semi-transient signals in the brain that persist for a while and are different than the usual equilibrium state. Gilbert Simondon invokes

108-413: A sense, an electron that happens to find itself in a metastable configuration is trapped there. Since transitions from a metastable state are not impossible (merely less likely), the electron will eventually decay to a less energetic state, typically by an electric quadrupole transition, or often by non-radiative de-excitation (e.g., collisional de-excitation). This slow-decay property of a metastable state

144-598: A single grain causes large parts of it to collapse. The avalanche is a well-known problem with large piles of snow and ice crystals on steep slopes. In dry conditions, snow slopes act similarly to sandpiles. An entire mountainside of snow can suddenly slide due to the presence of a skier, or even a loud noise or vibration. Aggregated systems of subatomic particles described by quantum mechanics ( quarks inside nucleons , nucleons inside atomic nuclei , electrons inside atoms , molecules , or atomic clusters ) are found to have many distinguishable states. Of these, one (or

180-493: A small degenerate set ) is indefinitely stable: the ground state or global minimum . All other states besides the ground state (or those degenerate with it) have higher energies. Of all these other states, the metastable states are the ones having lifetimes lasting at least 10 to 10 times longer than the shortest lived states of the set. A metastable state is then long-lived (locally stable with respect to configurations of 'neighbouring' energies) but not eternal (as

216-476: A system of atoms or molecules involving a change in chemical bond can be in a metastable state, which lasts for a relatively long period of time. Molecular vibrations and thermal motion make chemical species at the energetic equivalent of the top of a round hill very short-lived. Metastable states that persist for many seconds (or years) are found in energetic valleys which are not the lowest possible valley (point 1 in illustration). A common type of metastability

252-692: A thermodynamic trough without being at the lowest energy state is known as having kinetic stability or being kinetically persistent. The particular motion or kinetics of the atoms involved has resulted in getting stuck, despite there being preferable (lower-energy) alternatives. Metastable states of matter (also referred as metastates ) range from melting solids (or freezing liquids), boiling liquids (or condensing gases) and sublimating solids to supercooled liquids or superheated liquid-gas mixtures. Extremely pure, supercooled water stays liquid below 0 °C and remains so until applied vibrations or condensing seed doping initiates crystallization centers. This

288-429: A whole (see Metastable states of matter and grain piles below). The abundance of states is more prevalent as the systems grow larger and/or if the forces of their mutual interaction are spatially less uniform or more diverse. In dynamic systems (with feedback ) like electronic circuits, signal trafficking, decisional, neural and immune systems, the time-invariance of the active or reactive patterns with respect to

324-635: A zero enthalpy of formation . In base , white phosphorus spontaneously disproportionates to phosphine and various phosphorus oxyacid salts. Many reactions of white phosphorus involve insertion into the P-P bonds, such as the reaction with oxygen, sulfur, phosphorus tribromide and the NO ion . It ignites spontaneously in air at about 50 °C (122 °F), and at much lower temperatures if finely divided (due to melting-point depression ). Phosphorus reacts with oxygen, usually forming two oxides depending on

360-438: Is isomerisation . Higher energy isomers are long lived because they are prevented from rearranging to their preferred ground state by (possibly large) barriers in the potential energy . During a metastable state of finite lifetime, all state-describing parameters reach and hold stationary values. In isolation: The metastability concept originated in the physics of first-order phase transitions . It then acquired new meaning in

396-408: Is isomerism . The stability or metastability of a given chemical system depends on its environment, particularly temperature and pressure . The difference between producing a stable vs. metastable entity can have important consequences. For instances, having the wrong crystal polymorph can result in failure of a drug while in storage between manufacture and administration. The map of which state

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432-456: Is a common situation for the droplets of atmospheric clouds. Metastable phases are common in condensed matter and crystallography. This is the case for anatase , a metastable polymorph of titanium dioxide , which despite commonly being the first phase to form in many synthesis processes due to its lower surface energy , is always metastable, with rutile being the most stable phase at all temperatures and pressures. As another example, diamond

468-423: Is a stable phase only at very high pressures, but is a metastable form of carbon at standard temperature and pressure . It can be converted to graphite (plus leftover kinetic energy), but only after overcoming an activation energy – an intervening hill. Martensite is a metastable phase used to control the hardness of most steel. Metastable polymorphs of silica are commonly observed. In some cases, such as in

504-458: Is also used to refer to specific situations in mass spectrometry and spectrochemistry. A digital circuit is supposed to be found in a small number of stable digital states within a certain amount of time after an input change. However, if an input changes at the wrong moment a digital circuit which employs feedback (even a simple circuit such as a flip-flop ) can enter a metastable state and take an unbounded length of time to finally settle into

540-480: Is 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

576-423: Is apparent in phosphorescence , the kind of photoluminescence seen in glow-in-the-dark toys that can be charged by first being exposed to bright light. Whereas spontaneous emission in atoms has a typical timescale on the order of 10 seconds, the decay of metastable states can typically take milliseconds to minutes, and so light emitted in phosphorescence is usually both weak and long-lasting. In chemical systems,

612-405: Is characterised by lifetimes on the order of 10 years (as compared with the lifetime of the universe, which is thought to be around 1.3787 × 10 years). Sandpiles are one system which can exhibit metastability if a steep slope or tunnel is present. Sand grains form a pile due to friction . It is possible for an entire large sand pile to reach a point where it is stable, but the addition of

648-501: Is heated in an electric or fuel-fired furnace in the presence of carbon and silica . Elemental phosphorus is then liberated as a vapour and can be collected under phosphoric acid . An idealized equation for this carbothermal reaction is shown for calcium phosphate (although phosphate rock contains substantial amounts of fluoroapatite , which would also form silicon tetrafluoride ): In this way, an estimated 750,000 tons were produced in 1988. Most (83% in 1988) white phosphorus

684-416: Is one of allotropes of phosphorus . It is a translucent waxy solid that quickly yellows in light (due to its photochemical conversion into red phosphorus ), and impure white phosphorus is for this reason called yellow phosphorus. White phosphorus is the first allotrope of phosphorus, and in fact the first elementary substance to be discovered that was not known since ancient times. It glows greenish in

720-564: Is rather acutely toxic, with a lethal dose of 50-100 mg (1 mg/kg body weight). Its mode of action is thought to involve its reducing properties. It is metabolized to phosphate, which is not toxic. White phosphorus is used as a weapon because it is pyrophoric. For the same reasons, it is dangerous to handle. Measures are taken to protect samples from air. Anecdotal report of problems for beachcombers who may collect washed-up samples while unaware of their true nature. Metastability#Chemistry In chemistry and physics , metastability

756-437: Is the body-centered cubic α form, which is actually metastable under standard conditions . The β form is believed to have a hexagonal crystal structure. Molten and gaseous white phosphorus also retains the tetrahedral molecules, until 800 °C (1,500 °F; 1,100 K) when it starts decomposing to P 2 molecules. The P 4 molecule in the gas phase has a P-P bond length of r g = 2.1994(3) Å as

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792-413: Is the most stable as a function of pressure, temperature and/or composition is known as a phase diagram . In regions where a particular state is not the most stable, it may still be metastable. Reaction intermediates are relatively short-lived, and are usually thermodynamically unstable rather than metastable. The IUPAC recommends referring to these as transient rather than metastable. Metastability

828-478: Is used as a precursor to phosphoric acid, half of which is used for food or medical products where purity is important. The other half is used for detergents. Much of the remaining 17% is mainly used for the production of chlorinated compounds phosphorus trichloride , phosphorus oxychloride , and phosphorus pentachloride : Other products derived from white phosphorus include phosphorus pentasulfide and various metal phosphides. Although white phosphorus forms

864-480: Is used as a substrate for epitaxial optoelectronic devices based other semiconductors, such as indium gallium arsenide . The devices include pseudomorphic heterojunction bipolar transistors that could operate at 604 GHz. InP itself has a direct bandgap , making it useful for optoelectronics devices like laser diodes and photonic integrated circuits for the optical telecommunications industry, to enable wavelength-division multiplexing applications. It

900-467: Is used in high-power and high-frequency electronics because of its superior electron velocity with respect to the more common semiconductors silicon and gallium arsenide . InP is used in lasers, sensitive photodetectors and modulators in the wavelength window typically used for telecommunications, i.e., 1550 nm wavelengths, as it is a direct bandgap III-V compound semiconductor material. The wavelength between about 1510 nm and 1600 nm has

936-488: The allotropes of solid boron , acquiring a sample of the stable phase is difficult. The bonds between the building blocks of polymers such as DNA , RNA , and proteins are also metastable. Adenosine triphosphate (ATP) is a highly metastable molecule, colloquially described as being "full of energy" that can be used in many ways in biology. Generally speaking, emulsions / colloidal systems and glasses are metastable. The metastability of silica glass, for example,

972-560: The tetrahedron , the simplest possible Platonic hydrocarbon , no other polyhedral phosphorus clusters are known. White phosphorus converts to the thermodynamically-stabler red allotrope, but that allotrope is not isolated polyhedra. Cubane , in particular, is unlikely to form, and the closest approach is the half-phosphorus compound P 4 (CH) 4 , produced from phosphaalkynes . Other clusters are more thermodynamically favorable, and some have been partially formed as components of larger polyelemental compounds. White phosphorus

1008-435: The amount of available oxygen: P 4 O 6 ( phosphorus trioxide ) when reacted with a limited supply of oxygen, and P 4 O 10 when reacted with excess oxygen. On rare occasions, P 4 O 7 , P 4 O 8 , and P 4 O 9 are also formed, but in small amounts. This combustion gives phosphorus(V) oxide: The white allotrope can be produced using several methods. In the industrial process, phosphate rock

1044-445: The dark (when exposed to oxygen) and is highly flammable and pyrophoric (self-igniting) upon contact with air. It is toxic , causing severe liver damage on ingestion and phossy jaw from chronic ingestion or inhalation. The odour of combustion of this form has a characteristic garlic odor, and samples are commonly coated with white " diphosphorus pentoxide ", which consists of P 4 O 10 tetrahedra with oxygen inserted between

1080-414: The external influences defines stability and metastability (see brain metastability below). In these systems, the equivalent of thermal fluctuations in molecular systems is the " white noise " that affects signal propagation and the decision-making. Non-equilibrium thermodynamics is a branch of physics that studies the dynamics of statistical ensembles of molecules via unstable states. Being "stuck" in

1116-546: The global minimum is). Being excited – of an energy above the ground state – it will eventually decay to a more stable state, releasing energy. Indeed, above absolute zero , all states of a system have a non-zero probability to decay; that is, to spontaneously fall into another state (usually lower in energy). One mechanism for this to happen is through tunnelling . Some energetic states of an atomic nucleus (having distinct spatial mass, charge, spin, isospin distributions) are much longer-lived than others ( nuclear isomers of

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1152-476: The lowest attenuation available on optical fibre (about 0.2 dB/km). Further, O-band and C-band wavelengths supported by InP facilitate single-mode operation , reducing effects of intermodal dispersion . InP can be used in photonic integrated circuits that can generate, amplify, control and detect laser light. Optical sensing applications of InP include White phosphorus White phosphorus , yellow phosphorus , or simply tetraphosphorus (P 4 )

1188-604: The phosphorus atoms and at their vertices. White phosphorus is only slightly soluble in water and can be stored under water. P 4 is soluble in benzene , oils , carbon disulfide , and disulfur dichloride . White phosphorus exists as molecules of four phosphorus atoms in a tetrahedral structure, joined by six phosphorus—phosphorus single bonds . The tetrahedral arrangement results in ring strain and instability. Although both are called "white phosphorus", in fact two different crystal allotropes are known, interchanging reversibly at 195.2 K. The element's standard state

1224-604: The same isotope ), e.g. technetium-99m . The isotope tantalum-180m , although being a metastable excited state, is long-lived enough that it has never been observed to decay, with a half-life calculated to be least 4.5 × 10 years, over 3 million times the current age of the universe . Some atomic energy levels are metastable. Rydberg atoms are an example of metastable excited atomic states. Transitions from metastable excited levels are typically those forbidden by electric dipole selection rules . This means that any transitions from this level are relatively unlikely to occur. In

1260-469: The study of aggregated subatomic particles (in atomic nuclei or in atoms) or in molecules, macromolecules or clusters of atoms and molecules. Later, it was borrowed for the study of decision-making and information transmission systems. Metastability is common in physics and chemistry – from an atom (many-body assembly) to statistical ensembles of molecules ( viscous fluids , amorphous solids , liquid crystals , minerals , etc.) at molecular levels or as

1296-416: Was determined by gas electron diffraction . The β form of white phosphorus contains three slightly different P 4 molecules, i.e. 18 different P-P bond lengths — between 2.1768(5) and 2.1920(5) Å. The average P-P bond length is 2.183(5) Å. Despite white phosphorus not being the most stable allotropes of phosphorus, its molecular nature allows it to be easily purified. Thus, it's defined to have

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