Crystal

A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.[1][2] In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.

The word crystal derives from the Ancient Greek word κρύσταλλος (krustallos), meaning both "ice" and "rock crystal",[3] from κρύος (kruos), "icy cold, frost".[4][5]

Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most metals, rocks, ceramics, and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics.

Despite the name, lead crystal, crystal glass, and related products are not crystals, but rather types of glass, i.e. amorphous solids.

Crystals are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements.[6][7][8]

Amethystemadagascar2
A crystal of amethyst quartz
Crystalline polycrystalline amorphous2
Microscopically, a single crystal has atoms in a near-perfect periodic arrangement; a polycrystal is composed of many microscopic crystals (called "crystallites" or "grains"); and an amorphous solid (such as glass) has no periodic arrangement even microscopically.

Crystal structure (microscopic)

Sodium-chloride-3D-ionic
Microscopic structure of a Halite (mineral) crystal. (Purple is sodium ion, green is chlorine ion). There is cubic symmetry in the atoms' arrangement
Selpologne
Macroscopic (~16cm) halite crystal. The right-angles between crystal faces are due to the cubic symmetry of the atoms' arrangement

The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. A crystal is a solid where the atoms form a periodic arrangement. (Quasicrystals are an exception, see below).

Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals (called "crystallites" or "grains") is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries. Most macroscopic inorganic solids are polycrystalline, including almost all metals, ceramics, ice, rocks, etc. Solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids, also called glassy, vitreous, or noncrystalline. These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does.

A crystal structure (an arrangement of atoms in a crystal) is characterized by its unit cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal.

The symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries, called crystallographic space groups. These are grouped into 7 crystal systems, such as cubic crystal system (where the crystals may form cubes or rectangular boxes, such as Halite (mineral) shown at right) or hexagonal crystal system (where the crystals may form hexagons, such as ordinary water ice).

Crystal faces and shapes

Crystal facet formation
As a Halite (mineral) crystal is growing, new atoms can very easily attach to the parts of the surface with rough atomic-scale structure and many dangling bonds. Therefore, these parts of the crystal grow out very quickly (yellow arrows). Eventually, the whole surface consists of smooth, stable faces, where new atoms cannot as easily attach themselves.

Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see.

Euhedral crystals are those with obvious, well-formed flat faces. Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid.

The flat faces (also called facets) of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: they are planes of relatively low Miller index.[9] This occurs because some surface orientations are more stable than others (lower surface energy). As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.)

One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying crystal symmetry.

A crystal's habit is its visible external shape. This is determined by the crystal structure (which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed.

Occurrence in nature

Ice crystals
Ice crystals
CalciteEchinosphaerites
Fossil shell with calcite crystals

Rocks

By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock. Crystals found in rocks typically range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. As of 1999, the world's largest known naturally occurring crystal is a crystal of beryl from Malakialina, Madagascar, 18 m (59 ft) long and 3.5 m (11 ft) in diameter, and weighing 380,000 kg (840,000 lb).[10]

Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock. The vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends primarily on the conditions under which they solidified. Such rocks as granite, which have cooled very slowly and under great pressures, have completely crystallized; but many kinds of lava were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or glassy matter is common. Other crystalline rocks, the metamorphic rocks such as marbles, mica-schists and quartzites, are recrystallized. This means that they were at first fragmental rocks like limestone, shale and sandstone and have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state.[11]

Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins. Evaporites such as Halite (mineral), gypsum and some limestones have been deposited from aqueous solution, mostly owing to evaporation in arid climates.

Ice

Water-based ice in the form of snow, sea ice and glaciers is a very common manifestation of crystalline or polycrystalline matter on Earth. A single snowflake is a single crystal or a collection of crystals,[12] while an ice cube is a polycrystal.[13]

Organigenic crystals

Many living organisms are able to produce crystals, for example calcite and aragonite in the case of most molluscs or hydroxylapatite in the case of vertebrates.

Polymorphism and allotropy

The same group of atoms can often solidify in many different ways. Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water ice is ordinarily found in the hexagonal form Ice Ih, but can also exist as the cubic Ice Ic, the rhombohedral ice II, and many other forms. The different polymorphs are usually called different phases.

In addition, the same atoms may be able to form noncrystalline phases. For example, water can also form amorphous ice, while SiO2 can form both fused silica (an amorphous glass) and quartz (a crystal). Likewise, if a substance can form crystals, it can also form polycrystals.

For pure chemical elements, polymorphism is known as allotropy. For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have wildly different properties. For example, diamond is among the hardest substances known, while graphite is so soft that it is used as a lubricant.

Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form.

Crystallization

1-cooling-crystallizer-schladen
Vertical cooling crystallizer in a beet sugar factory.

Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. (More rarely, crystals may be deposited directly from gas; see thin-film deposition and epitaxy.)

Crystallization is a complex and extensively-studied field, because depending on the conditions, a single fluid can solidify into many different possible forms. It can form a single crystal, perhaps with various possible phases, stoichiometries, impurities, defects, and habits. Or, it can form a polycrystal, with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the ambient pressure, the temperature, and the speed with which all these parameters are changing.

Specific industrial techniques to produce large single crystals (called boules) include the Czochralski process and the Bridgman technique. Other less exotic methods of crystallization may be used, depending on the physical properties of the substance, including hydrothermal synthesis, sublimation, or simply solvent-based crystallization.

Large single crystals can be created by geological processes. For example, selenite crystals in excess of 10 meters are found in the Cave of the Crystals in Naica, Mexico.[14] For more details on geological crystal formation, see above.

Crystals can also be formed by biological processes, see above. Conversely, some organisms have special techniques to prevent crystallization from occurring, such as antifreeze proteins.

Defects, impurities, and twinning

Vector de Burgers
Two types of crystallographic defects. Top right: edge dislocation. Bottom right: screw dislocation.

An ideal crystal has every atom in a perfect, exactly repeating pattern.[15] However, in reality, most crystalline materials have a variety of crystallographic defects, places where the crystal's pattern is interrupted. The types and structures of these defects may have a profound effect on the properties of the materials.

A few examples of crystallographic defects include vacancy defects (an empty space where an atom should fit), interstitial defects (an extra atom squeezed in where it does not fit), and dislocations (see figure at right). Dislocations are especially important in materials science, because they help determine the mechanical strength of materials.

Another common type of crystallographic defect is an impurity, meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of diamond would only contain carbon atoms, but a real crystal might perhaps contain a few boron atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal.

Pyrite 60608
Twinned pyrite crystal group.

In semiconductors, a special type of impurity, called a dopant, drastically changes the crystal's electrical properties. Semiconductor devices, such as transistors, are made possible largely by putting different semiconductor dopants into different places, in specific patterns.

Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way.

Mosaicity is a spread of crystal plane orientations. A mosaic crystal is supposed to consist of smaller crystalline units that are somewhat misaligned with respect to each other.

Chemical bonds

In general, solids can be held together by various types of chemical bonds, such as metallic bonds, ionic bonds, covalent bonds, van der Waals bonds, and others. None of these are necessarily crystalline or non-crystalline. However, there are some general trends as follows.

Metals are almost always polycrystalline, though there are exceptions like amorphous metal and single-crystal metals. The latter are grown synthetically. (A microscopically-small piece of metal may naturally form into a single crystal, but larger pieces generally do not.) Ionic compound materials are usually crystalline or polycrystalline. In practice, large salt crystals can be created by solidification of a molten fluid, or by crystallization out of a solution. Covalently bonded solids (sometimes called covalent network solids) are also very common, notable examples being diamond and quartz. Weak van der Waals forces also help hold together certain crystals, such as crystalline molecular solids, as well as the interlayer bonding in graphite. Polymer materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous.

Quasicrystals

Ho-Mg-ZnQuasicrystal
The material holmium–magnesium–zinc (Ho–Mg–Zn) forms quasicrystals, which can take on the macroscopic shape of a dodecahedron. (Only a quasicrystal, not a normal crystal, can take this shape.) The edges are 2 mm long.

A quasicrystal consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in x-ray diffraction, and the ability to form shapes with smooth, flat faces.

Quasicrystals are most famous for their ability to show five-fold symmetry, which is impossible for an ordinary periodic crystal (see crystallographic restriction theorem).

The International Union of Crystallography has redefined the term "crystal" to include both ordinary periodic crystals and quasicrystals ("any solid having an essentially discrete diffraction diagram"[16]).

Quasicrystals, first discovered in 1982, are quite rare in practice. Only about 100 solids are known to form quasicrystals, compared to about 400,000 periodic crystals known in 2004.[17] The 2011 Nobel Prize in Chemistry was awarded to Dan Shechtman for the discovery of quasicrystals.[18]

Special properties from anisotropy

Crystals can have certain special electrical, optical, and mechanical properties that glass and polycrystals normally cannot. These properties are related to the anisotropy of the crystal, i.e. the lack of rotational symmetry in its atomic arrangement. One such property is the piezoelectric effect, where a voltage across the crystal can shrink or stretch it. Another is birefringence, where a double image appears when looking through a crystal. Moreover, various properties of a crystal, including electrical conductivity, electrical permittivity, and Young's modulus, may be different in different directions in a crystal. For example, graphite crystals consist of a stack of sheets, and although each individual sheet is mechanically very strong, the sheets are rather loosely bound to each other. Therefore, the mechanical strength of the material is quite different depending on the direction of stress.

Not all crystals have all of these properties. Conversely, these properties are not quite exclusive to crystals. They can appear in glasses or polycrystals that have been made anisotropic by working or stress—for example, stress-induced birefringence.

Crystallography

Crystallography is the science of measuring the crystal structure (in other words, the atomic arrangement) of a crystal. One widely used crystallography technique is X-ray diffraction. Large numbers of known crystal structures are stored in crystallographic databases.

Image gallery

Hoar frost macro2

Hoar frost: A type of ice crystal (picture taken from a distance of about 5 cm).

Gallium crystals

Gallium, a metal that easily forms large crystals.

Apatite-Rhodochrosite-Fluorite-169799

An apatite crystal sits front and center on cherry-red rhodochroite rhombs, purple fluorite cubes, quartz and a dusting of brass-yellow pyrite cubes.

Monokristalines Silizium für die Waferherstellung

Boules of silicon, like this one, are an important type of industrially-produced single crystal.

Bornite-Chalcopyrite-Pyrite-180794

A specimen consisting of a bornite-coated chalcopyrite crystal nestled in a bed of clear quartz crystals and lustrous pyrite crystals. The bornite-coated crystal is up to 1.5 cm across.

See also

References

  1. ^ Stephen Lower. "Chem1 online textbook—States of matter". Retrieved 2016-09-19.
  2. ^ Ashcroft and Mermin (1976). Solid state physics.CS1 maint: Uses authors parameter (link)
  3. ^ κρύσταλλος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
  4. ^ κρύος, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
  5. ^ "The American Heritage Dictionary of the English Language". Kreus. 2000.CS1 maint: others (link)
  6. ^ Regal, Brian. (2009). Pseudoscience: A Critical Encyclopedia. Greenwood. p. 51. ISBN 978-0-313-35507-3
  7. ^ Patti Wigington (31 August 2016). "Using Crystals and Gemstones in Magic". About.com. Retrieved 14 November 2016.
  8. ^ "The Magic of Crystals and Gemstones". WitchesLore. 14 December 2011. Retrieved 14 November 2016.
  9. ^ The surface science of metal oxides, by Victor E. Henrich, P. A. Cox, page 28, google books link
  10. ^ G. Cressey and I. F. Mercer, (1999) Crystals, London, Natural History Museum, page 58
  11. ^  One or more of the preceding sentences incorporates text from a publication now in the public domainFlett, John Smith (1911). "Petrology" . In Chisholm, Hugh (ed.). Encyclopædia Britannica. 21 (11th ed.). Cambridge University Press.
  12. ^ Libbrecht, Kenneth; Wing, Rachel (2015-09-01). The Snowflake: Winter's Frozen Artistry. Voyageur Press. ISBN 9781627887335.
  13. ^ Hjorth-Hansen, E. (2017-10-19). Snow Engineering 2000: Recent Advances and Developments. Routledge. ISBN 9781351416238.
  14. ^ "Cave of Crystal Giants — National Geographic Magazine". nationalgeographic.com.
  15. ^ Britain), Science Research Council (Great (1972). Report of the Council. H.M. Stationery Office.
  16. ^ International Union of Crystallography (1992). "Report of the Executive Committee for 1991". Acta Crystallogr. A. 48 (6): 922. doi:10.1107/S0108767392008328. PMC 1826680.
  17. ^ Steurer W. (2004). "Twenty years of structure research on quasicrystals. Part I. Pentagonal, octagonal, decagonal and dodecagonal quasicrystals". Z. Kristallogr. 219 (7–2004): 391–446. Bibcode:2004ZK....219..391S. doi:10.1524/zkri.219.7.391.35643.
  18. ^ "The Nobel Prize in Chemistry 2011". Nobelprize.org. Retrieved 2011-12-29.

Further reading

Alan Pardew

Alan Scott Pardew (born 18 July 1961) is an English football manager and former professional footballer.

Pardew's highest achievements in the sport include reaching the FA Cup Final three times, as a player with Crystal Palace in 1990 and as a manager with West Ham United in 2006 and in 2016 when his Crystal Palace side lost to Manchester United. He has also achieved promotion three times in his career, as a player with Palace and as a manager with Reading and West Ham. He managed Newcastle United from 2010 to 2014.

As manager of Newcastle, Pardew won both the Premier League Manager of the Season and the LMA Manager of the Year awards for the 2011–12 season after guiding the Magpies to European football for the first time since the club's return to the Premier League.

On 22 December 2016, Pardew was dismissed as manager of Crystal Palace after a poor run of results. Pardew was a Sky Sports pundit for the 2017–18 Premier League season, before taking the West Bromwich Albion job after Tony Pulis was dismissed. On 2 April 2018, Pardew left West Brom by mutual consent.

Billy Crystal

William Edward Crystal (born March 14, 1948) is an American actor, comedian, writer, producer, director, and television host. He gained prominence in the 1970s and 80s for television roles as Jodie Dallas on the ABC sitcom Soap and as a cast member and frequent host of Saturday Night Live. He then became a Hollywood film star during the late 1980s and 1990s, appearing in the critical and box office successes The Princess Bride (1987), Throw Momma from the Train (1987), When Harry Met Sally... (1989), City Slickers (1991), Mr. Saturday Night (1992) and Analyze This (1999), and providing the voice of Mike Wazowski in the Monsters, Inc. films starting in 2001.

He has hosted the Academy Awards nine times, beginning in 1990 and most recently in 2012.

Crystal Palace, London

Crystal Palace is an area in South London, England, named after the Crystal Palace Exhibition building which stood in the area from 1854 until it was destroyed by fire in 1936. Approximately

7 miles southeast of Charing Cross, it includes one of the highest points in London, at 367 feet (112 m), offering views over the capital. The area has no defined boundaries and straddles five London boroughs and three postal districts, although there is a Crystal Palace electoral ward and Crystal Palace Park in the London Borough of Bromley. It is contiguous with Anerley, Dulwich Wood, Gipsy Hill, Penge, South Norwood, Sydenham and Upper Norwood.

The district was a natural oak forest until development began in the 19th century, and before the arrival of the Crystal Palace, it was known as Sydenham Hill. The Norwood Ridge and an historic oak tree were used to mark parish boundaries. The area is represented by three parliamentary constituencies, four London Assembly constituencies and fourteen local councillors. After the Crystal Palace burned down in 1936, the site of the building and its grounds became Crystal Palace Park, the location of the National Sports Centre which contains an athletics track, stadium and other sports facilities. Crystal Palace Park has also been used as the setting for a number of concerts and films, such as The Italian Job and The Pleasure Garden and contains the Crystal Palace Park Concert Platform, in place since 1997. Two television transmitter masts make the district a landmark location, visible from many parts of Greater London. Local landmarks include the Crystal Palace Triangle, a shopping district made up of three streets forming a triangle; Westow Park, a smaller park that lies off the triangle to the south west of Crystal Palace Park; and the Stambourne Woodland Walk.

A pneumatic railway was briefly trialed in the area in 1864. Once the railways arrived, Crystal Palace was eventually served by two railway stations, the high level and low level stations, built to handle the large volume of passengers visiting the exhibition building. After the palace was destroyed by fire, and with railway travel declining, passenger numbers fell and the high level station was closed in 1954 and demolished 7 years later. Rail services gradually declined, and for a period in the 1960s and 1970s, there were plans to construct an urban motorway through the area as part of the London Ringways plan. With rising passenger numbers, additional London Overground services began stopping at the station and a major station redevelopment in 2012 led to proposals to extend the Croydon Tramlink service to the railway and bus stations. In 2016, Crystal Palace was named one of the best places to live in London.

Crystal Palace F.C.

Crystal Palace Football Club is an English professional football club based in Selhurst, South London, that competes in the Premier League, the highest level of English football. They were founded in 1905 at the famous Crystal Palace Exhibition building and played their home games at the FA Cup Final stadium situated inside the historic Palace grounds. The club were forced to leave the Palace in 1915 due to the outbreak of the First World War, and played at Herne Hill Velodrome and the Nest until 1924, when they moved to their current home at Selhurst Park.

The club spent its early years in the Southern League before joining the Football League in 1920, where they became inaugural champions of the newly formed Third Division in 1920–21. Since 1964, Palace have mainly played in the top two leagues of English football and have only dropped below the second tier once, for three seasons between 1974 and 1977. During the late 1980s and early 1990s, Palace became a force in the top flight, and challenged for the League title in 1990–91, eventually finishing in third place, their highest league position to date, and were only denied a place in Europe because of the partial UEFA ban on English clubs at that time following the Heysel Stadium disaster. Palace also reached the 1990 FA Cup Final. The club were one of the original founding members of the Premier League. Palace set two unwanted Premier League records for relegation, in 1992–93 they were relegated on 49 points, which is still a record number of points for a relegated Premier League club and are also the only club ever to be relegated from the Premier League even though they finished fourth from bottom in 1994–95, as it had been decided that at the end of that season the Premier League would be reduced in size from 22 to 20 clubs. The club suffered severe financial problems towards the end of the 1990s and into the 2000s, and went into administration twice in 1999 and 2010. Palace recovered and gained promotion back to the Premier League in 2012–13 where they have remained ever since and they reached another FA Cup final in 2016.

The club's traditional kit colours were originally claret and blue, but in 1973 they decided to change to the red and blue vertical stripes now worn today. Palace have a fierce rivalry with Brighton & Hove Albion, with whom they contest the M23 derby and also share rivalries with fellow South London clubs Millwall and Charlton Athletic.

Crystal structure

In crystallography, crystal structure is a description of the ordered arrangement of atoms, ions or molecules in a crystalline material. Ordered structures occur from the intrinsic nature of the constituent particles to form symmetric patterns that repeat along the principal directions of three-dimensional space in matter.

The smallest group of particles in the material that constitutes this repeating pattern is the unit cell of the structure. The unit cell completely reflects the symmetry and structure of the entire crystal, which is built up by repetitive translation of the unit cell along its principal axes. The translation vectors define the nodes of the Bravais lattice.

The lengths of the principal axes, or edges, of the unit cell and the angles between them are the lattice constants, also called lattice parameters or cell parameters. The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space may be described by the 230 space groups.

The crystal structure and symmetry play a critical role in determining many physical properties, such as cleavage, electronic band structure, and optical transparency.

Cubic crystal system

In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.

There are three main varieties of these crystals:

Primitive cubic (abbreviated cP and alternatively called simple cubic)

Body-centered cubic (abbreviated cI or bcc)

Face-centered cubic (abbreviated cF or fcc, and alternatively called cubic close-packed or ccp)Each is subdivided into other variants listed below. Note that although the unit cell in these crystals is conventionally taken to be a cube, the primitive unit cell often is not.

EFL Championship play-offs

The English Football League Championship play-offs are a series of play-off matches contested by the teams finishing from 3rd to 6th in the EFL Championship table. The semi-finals are played over two legs, with 3rd playing 6th and 4th playing 5th, with the return fixtures following. The final is played at Wembley Stadium, although from 2001 to 2006, it was played at the Millennium Stadium in Cardiff while Wembley was being rebuilt.

The first play-offs at this level were contested in 1987, when it was the Football League Second Division. From 1993 to 2004, following the creation of the FA Premier League as a breakaway from the Football League, it became the Division One play-offs, and since 2005 has taken its current name as the Championship play-offs following a rebranding of the remaining three divisions of the Football League.

There is no single sporting event in the world more valuable to the winners, who end up approximately £60m better off than the losers, mainly due to the increased commercial television revenue from being promoted to the Premier League. However, by convention the two finalists agree that the loser will keep all the gate receipts from the game, so as to slightly soften the financial blow of missing out.The most recent final was between Fulham and Aston Villa on 26 May 2018, with Fulham being promoted to the Premier League after a 1-0 victory.

Ipswich Town have been in the Championship play-offs a record eight times: 1987, 1997–2000 inclusive, 2004, 2005 and 2015, making the final only once in 2000 (when they won promotion). Leicester City have reached the Championship play-off final four times (in the space of five seasons), losing two in 1992 and 1993 and winning two in 1994 and 1996. Crystal Palace have also appeared in the final five times, losing in 1996 and winning in 1989, 1997, 2004 and 2013, the most wins by any club.The team finishing highest in the league (third) has succeeded in winning promotion eleven times out of thirty seasons, up to 2017, with 4th managing six promotions, 5th eight and 6th five.

The play-off winners have managed to finish above the Championship winners and runners-up in the subsequent Premier League season on seven occasions: Blackburn Rovers in 1992–93, Leicester City in 1996–97, Ipswich Town in 2000–01, West Ham United in 2005–06 and 2012–13, Swansea City in 2011–12, and Crystal Palace in 2013–14.

Great Exhibition

The Great Exhibition of the Works of Industry of All Nations or The Great Exhibition (sometimes referred to as the Crystal Palace Exhibition in reference to the temporary structure in which it was held), an international exhibition, took place in Hyde Park, London, from 1 May to 15 October 1851. It was the first in a series of World's Fairs, exhibitions of culture and industry that became popular in the 19th century, and it was a much anticipated event. The Great Exhibition was organized by Henry Cole and by Prince Albert, husband of the reigning monarch of the United Kingdom, Queen Victoria. Famous people of the time attended, including Charles Darwin, Samuel Colt, members of the Orléanist Royal Family and the writers Charlotte Brontë, Charles Dickens, Lewis Carroll, George Eliot, Alfred Tennyson and William Makepeace Thackeray.

Indiana Jones and the Kingdom of the Crystal Skull

Indiana Jones and the Kingdom of the Crystal Skull is a 2008 American action-adventure film directed by Steven Spielberg and the fourth installment in the Indiana Jones series. Released nineteen years after the previous film, the film is set in 1957, pitting Indiana Jones (Harrison Ford) against Soviet agents—led by Irina Spalko (Cate Blanchett)—searching for a telepathic crystal skull. Jones is aided by his former lover, Marion Ravenwood (Karen Allen), and her son, Mutt Williams (Shia LaBeouf). Ray Winstone, John Hurt, and Jim Broadbent are also part of the supporting cast.

Screenwriters Jeb Stuart, Jeffrey Boam, Frank Darabont, and Jeff Nathanson wrote drafts before David Koepp's script satisfied the producers. The filmmakers intended to pay tribute to the science fiction B-movies of the 1950s era. Shooting began on June 18, 2007, at various locations in New Mexico, New Haven, Connecticut, Hawaii, and Fresno, California, as well as on sound stages in Los Angeles. To maintain aesthetic continuity with the previous films, the crew relied on traditional stunt work instead of computer-generated stunt doubles, and cinematographer Janusz Kamiński studied Douglas Slocombe's style from the previous films.

The film premiered at the 2008 Cannes Film Festival on May 18, 2008, and was released worldwide on May 22, 2008 to generally positive reviews with praise for the performances, action scenes, John Williams' musical score, and the costume design. Criticism, however, focused on the dialogue, storyline, pacing, and overuse of CGI. It was also a financial success like the previous three films in the series, grossing over $786 million worldwide, becoming the franchise's highest-grossing film when not adjusted for inflation, as well as the second-highest-grossing film of 2008. The film is scheduled to be followed by an untitled fifth film, planned for release on July 9, 2021, with both Spielberg and Ford returning.

League of Legends

League of Legends (abbreviated LoL) is a multiplayer online battle arena video game developed and published by Riot Games for Microsoft Windows and macOS. The game follows a freemium model and is supported by microtransactions, and was inspired by the Warcraft III: The Frozen Throne mod, Defense of the Ancients.In League of Legends, players assume the role of an unseen "summoner" that controls a "champion" with unique abilities and battle against a team of other players or computer-controlled champions. The goal is usually to destroy the opposing team's "Nexus", a structure that lies at the heart of a base protected by defensive structures, although other distinct game modes exist as well. Each League of Legends match is discrete, with all champions starting off fairly weak but increases in strength by accumulating items and experience over the course of the game. The champions and setting blend a variety of elements, including high fantasy, steampunk, and Lovecraftian horror.

League of Legends was generally well received upon its release in 2009, and has since grown in popularity, with an active and expansive fanbase. By July 2012, League of Legends was the most played PC game in North America and Europe in terms of the number of hours played. In January 2014, over 67 million people played League of Legends per month, 27 million per day, and over 7.5 million concurrently during peak hours. League has among the largest footprints of any game in streaming media communities on platforms such as YouTube and Twitch.tv; it routinely ranks first in the most-watched hours. In September 2016, the company estimated that there are over 100 million active players each month. The game's popularity has led it to expand into merchandise, with toys, accessories, apparel, as well as tie-ins to other media through music videos, web series, documentaries, and books.

League of Legends has an active and widespread competitive scene. In North America and Europe, Riot Games organizes the League Championship Series (LCS), located in Los Angeles and Berlin respectively, which consists of 10 professional teams in each continent. Similar regional competitions exist in China (LPL), South Korea (LCK), Taiwan/Hong Kong/Macau (LMS), and various other regions. These regional competitions culminate with the annual World Championship. The 2017 World Championship had 60 million unique viewers and a total prize pool of over US$4 million. The 2018 Mid-Season Invitational had an overall peak concurrent viewership of 19.8 million, while the finals had an average concurrent viewership of 11 million.

Liquid-crystal display

A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in colour or monochrome. LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden, such as preset words, digits, and seven-segment displays, as in a digital clock. They use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. Optical filters are added to white on blue LCDs to give them their characteristic appearance.

LCDs are used in a wide range of applications, including LCD televisions, computer monitors, instrument panels, aircraft cockpit displays, and indoor and outdoor signage. Small LCD screens are common in portable consumer devices such as digital cameras, watches, calculators, and mobile telephones, including smartphones. LCD screens are also used on consumer electronics products such as DVD players, video game devices and clocks. LCD screens have replaced heavy, bulky cathode ray tube (CRT) displays in nearly all applications. LCD screens are available in a wider range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to very large television receivers. LCDs are slowly being replaced by OLEDs, which can be easily made into different shapes, and have a lower response time, wider color gamut, virtually infinite color contrast and viewing angles, lower weight for a given display size and a slimmer profile (because OLEDs use a single glass or plastic panel whereas LCDs use two glass panels; the thickness of the panels increases with size but the increase is more noticeable on LCDs) and potentially lower power consumption (as the display is only "on" where needed and there is no backlight). OLEDs, however, are more expensive for a given display size due to the very expensive electroluminescent materials or phosphors that they use. Also due to the use of phosphors, OLEDs suffer from screen burn-in and there is currently no way to recycle OLED displays, whereas LCD panels can be recycled, although the technology required to recycle LCDs is not yet widespread. Attempts to increase the lifespan of LCDs are quantum dot displays, which offer similar performance as an OLED display, but the Quantum dot sheet that gives these displays their characteristics can not yet be recycled.

Since LCD screens do not use phosphors, they rarely suffer image burn-in when a static image is displayed on a screen for a long time, e.g., the table frame for an airline flight schedule on an indoor sign. LCDs are, however, susceptible to image persistence. The LCD screen is more energy-efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery-powered electronic equipment more efficiently than CRTs can be. By 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes.

Methamphetamine

Methamphetamine (contracted from N-methylamphetamine) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder and obesity. Methamphetamine was discovered in 1893 and exists as two enantiomers: levo-methamphetamine and dextro-methamphetamine. Methamphetamine properly refers to a specific chemical, the racemic free base, which is an equal mixture of levomethamphetamine and dextromethamphetamine in their pure amine forms. It is rarely prescribed over concerns involving human neurotoxicity and potential for recreational use as an aphrodisiac and euphoriant, among other concerns, as well as the availability of safer substitute drugs with comparable treatment efficacy. Dextromethamphetamine is a much stronger CNS stimulant than levomethamphetamine.

Both methamphetamine and dextromethamphetamine are illicitly trafficked and sold owing to their potential for recreational use. The highest prevalence of illegal methamphetamine use occurs in parts of Asia, Oceania, and in the United States, where racemic methamphetamine, levomethamphetamine, and dextromethamphetamine are classified as schedule II controlled substances. Levomethamphetamine is available as an over-the-counter (OTC) drug for use as an inhaled nasal decongestant in the United States. Internationally, the production, distribution, sale, and possession of methamphetamine is restricted or banned in many countries, due to its placement in schedule II of the United Nations Convention on Psychotropic Substances treaty. While dextromethamphetamine is a more potent drug, racemic methamphetamine is sometimes illicitly produced due to the relative ease of synthesis and limited availability of chemical precursors.

In low to moderate doses, methamphetamine can elevate mood, increase alertness, concentration and energy in fatigued individuals, reduce appetite, and promote weight loss. At very high doses, it can induce psychosis, breakdown of skeletal muscle, seizures and bleeding in the brain. Chronic high-dose use can precipitate unpredictable and rapid mood swings, stimulant psychosis (e.g., paranoia, hallucinations, delirium, and delusions) and violent behavior. Recreationally, methamphetamine's ability to increase energy has been reported to lift mood and increase sexual desire to such an extent that users are able to engage in sexual activity continuously for several days. Methamphetamine is known to possess a high addiction liability (i.e., a high likelihood that long-term or high dose use will lead to compulsive drug use) and high dependence liability (i.e. a high likelihood that withdrawal symptoms will occur when methamphetamine use ceases). Heavy recreational use of methamphetamine may lead to a post-acute-withdrawal syndrome, which can persist for months beyond the typical withdrawal period. Unlike amphetamine, methamphetamine is neurotoxic to human midbrain dopaminergic neurons. It has also been shown to damage serotonin neurons in the CNS. This damage includes adverse changes in brain structure and function, such as reductions in grey matter volume in several brain regions and adverse changes in markers of metabolic integrity.

Methamphetamine belongs to the substituted phenethylamine and substituted amphetamine chemical classes. It is related to the other dimethylphenethylamines as a positional isomer of these compounds, which share the common chemical formula: C10H15N1.

Method Man

Clifford M. Smith (born March 2, 1971), better known by his stage name Method Man, is an American rapper, record producer and actor. He is known as a member of the East Coast hip hop collective Wu-Tang Clan. He is also one half of the hip hop duo Method Man & Redman. He took his stage name from the 1979 film Method Man. In 1996, Smith won a Grammy Award for Best Rap Performance by a Duo or Group, for "I'll Be There for You/You're All I Need to Get By", featuring American R&B singer Mary J. Blige.

Smith has appeared in films such as Belly (1998), How High (2001), Garden State (2004), The Wackness (2008), Venom (2005), Red Tails (2012), Keanu (2016), and The Cobbler (2014). On television, he and frequent collaborator, fellow East Coast rapper Redman, co-starred on the short-lived Fox sitcom Method & Red. He has also had recurring roles in three HBO series, as Tug Daniels in Oz, Melvin "Cheese" Wagstaff in The Wire, and Rodney in The Deuce, and a cameo role in Luke Cage (2016), which aired on Netflix.

Quartz

Quartz is a mineral composed of silicon and oxygen atoms in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K). Since the transformation is accompanied by a significant change in volume, it can easily induce fracturing of ceramics or rocks passing through this temperature threshold.

There are many different varieties of quartz, several of which are semi-precious gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Eurasia.

Sailor Moon

Sailor Moon (美少女戦士セーラームーン, Bishōjo Senshi Sērā Mūn, originally translated as Pretty Soldier Sailor Moon and later as Pretty Guardian Sailor Moon) is a Japanese shōjo manga series written and illustrated by Naoko Takeuchi. It was originally serialized in Nakayoshi from 1991 to 1997; the 60 individual chapters were published in 18 tankōbon volumes. The series follows the adventures of a schoolgirl named Usagi Tsukino as she transforms into Sailor Moon to search for a magical artifact, the "Legendary Silver Crystal" (「幻の銀水晶」, Maboroshi no Ginzuishō, lit. "Phantom Silver Crystal"). She leads a diverse group of comrades, the Sailor Soldiers (セーラー戦士, Sērā Senshi) (Sailor Guardians in later editions) as they battle against villains to prevent the theft of the Silver Crystal and the destruction of the Solar System.

The manga was adapted into an anime series produced by Toei Animation and broadcast in Japan from 1992 to 1997. Toei also developed three animated feature films, a television special, and three short films based on the anime. A live-action television adaptation, Pretty Guardian Sailor Moon, aired from 2003 to 2004, and a second anime series, Sailor Moon Crystal, began simulcasting in 2014. The manga series was licensed for an English language release by Kodansha Comics in North America, and in Australia and New Zealand by Random House Australia. The entire anime series has been licensed by Viz Media for an English language release in North America and by Madman Entertainment in Australia and New Zealand.

Since its release, Pretty Soldier Sailor Moon has received acclaim, with praise for its art, characterization, and humor. The manga has sold over 35 million copies worldwide, making it one of the best-selling shōjo manga series. The franchise has also generated $5 billion in merchandise sales.

The Crystal Palace

The Crystal Palace was a cast-iron and plate-glass structure originally built in Hyde Park, London, to house the Great Exhibition of 1851. The exhibition took place from 1 May until 15 October 1851, and more than 14,000 exhibitors from around the world gathered in its 990,000 square feet (92,000 m2) exhibition space to display examples of technology developed in the Industrial Revolution. Designed by Joseph Paxton, the Great Exhibition building was 1,851 feet (564 m) long, with an interior height of 128 feet (39 m). It was three times the size of St Paul's Cathedral.The introduction of the sheet glass method into Britain by Chance Brothers in 1832 made possible the production of large sheets of cheap but strong glass, and its use in the Crystal Palace created a structure with the greatest area of glass ever seen in a building. It astonished visitors with its clear walls and ceilings that did not require interior lights.

It has been suggested that the name of the building resulted from a piece penned by the playwright Douglas Jerrold, who in July 1850 wrote in the satirical magazine Punch about the forthcoming Great Exhibition, referring to a "palace of very crystal".After the exhibition, the Palace was relocated to an area of South London known as Penge Common. It was rebuilt at the top of Penge Peak next to Sydenham Hill, an affluent suburb of large villas. It stood there from June 1854 until its destruction by fire in November 1936. The nearby residential area was renamed Crystal Palace after the landmark. This included the Crystal Palace Park that surrounds the site, home of the Crystal Palace National Sports Centre, which had previously been a football stadium that hosted the FA Cup Final between 1895 and 1914. Crystal Palace F.C. were founded at the site in 1905 and played at the Cup Final venue in their early years. The park still contains Benjamin Waterhouse Hawkins's Crystal Palace Dinosaurs which date back to 1854.

The Dark Crystal

The Dark Crystal is a 1982 puppet animated high fantasy adventure film directed by Jim Henson and Frank Oz. It stars the voices of Stephen Garlick, Lisa Maxwell, Billie Whitelaw, Percy Edwards, and Barry Dennen. The film was produced by ITC Entertainment and Henson Associates and distributed by Universal Pictures. The plot revolves around Jen, an elf-like "Gelfling" on a quest to restore balance to his alien world by returning the lost shard of a powerful but broken gem.

It was marketed as a family film but was notably darker than the creators' previous material. The animatronics used in the film were considered groundbreaking. The primary concept artist was fantasy illustrator Brian Froud, famous for his distinctive fairy and dwarf designs. Froud also collaborated with Henson and Oz for their next project, the 1986 film Labyrinth.

The Dark Crystal was produced by Gary Kurtz, while the screenplay was written by David Odell, with whom Henson previously worked as a staff writer for The Muppet Show. The film score was composed by Trevor Jones. The film received mixed to positive reviews from mainstream critics; while being criticized for its darker, more dramatic tone in contrast to Henson‘s previous works, it was praised for its narrative, aesthetic, and characters, and has garnered a cult following in recent years. A prequel television series, The Dark Crystal: Age of Resistance, will premiere on Netflix on August 30, 2019.

Wilfried Zaha

Dazet Wilfried Armel Zaha (born 10 November 1992) is a professional footballer who plays as a forward for Premier League club Crystal Palace and the Ivorian national team.

Zaha advanced into the Crystal Palace first team from their academy, in 2010. In January 2013, he transferred to Manchester United for an initial fee of £10 million, Alex Ferguson's last transfer before his retirement at the end of the season. Zaha remained on loan at Palace until the end of the season, helping them return to the Premier League. After an unsuccessful 2013–14 season with Manchester United (partly spent on loan at Cardiff City), Zaha returned to Palace in August 2014 on a season-long loan, before rejoining the club on a permanent basis in February 2015.

Born in the Ivory Coast, Zaha grew up in England from the age of four. He made his debut for the England national team in 2012. He made two non-competitive appearances for England, the latter of which came in 2013, before switching his allegiances to the Ivory Coast ahead of the 2017 Africa Cup of Nations.

X-ray crystallography

X-ray crystallography (XRC) is a technique used for 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 various materials, especially minerals and alloys. The method also revealed the structure and function of many biological molecules, including vitamins, drugs, proteins and nucleic acids such as DNA. X-ray crystallography is still the primary method for characterizing the atomic structure of new materials and in discerning materials that appear similar by other experiments. X-ray crystal structures can also account for unusual electronic or elastic properties of a material, shed light on chemical interactions and processes, or serve as the basis for designing pharmaceuticals against diseases.

In a single-crystal X-ray diffraction measurement, a crystal is mounted on a goniometer. The goniometer is used to position the crystal at selected orientations. The crystal is illuminated with a finely focused monochromatic beam of X-rays, producing a diffraction pattern of regularly spaced spots known as reflections. The two-dimensional images taken at different orientations are converted into a three-dimensional model of the density of electrons within the crystal using the mathematical method of Fourier transforms, combined with chemical data known for the sample. Poor resolution (fuzziness) or even errors may result if the crystals are too small, or not uniform enough in their internal makeup.

X-ray crystallography is related to several other methods for determining atomic structures. Similar diffraction patterns can be produced by scattering electrons or neutrons, which are likewise interpreted by Fourier transformation. If single crystals of sufficient size cannot be obtained, various other X-ray methods can be applied to obtain less detailed information; such methods include fiber diffraction, powder diffraction and (if the sample is not crystallized) small-angle X-ray scattering (SAXS).

If the material under investigation is only available in the form of nanocrystalline powders or suffers from poor crystallinity, the methods of electron crystallography can be applied for determining the atomic structure.

For all above mentioned X-ray diffraction methods, the scattering is elastic; the scattered X-rays have the same wavelength as the incoming X-ray. By contrast, inelastic X-ray scattering methods are useful in studying excitations of the sample such as plasmons, crystal-field and orbital excitations, magnons, and phonons, rather than the distribution of its atoms.

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