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Bravais Lattice
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Bravais lattice
In geometry and crystallography, a Bravais lattice, stud-ied by Auguste Bravais (1850),[1] is an innite array ofdiscrete points generated by a set of discrete translationoperations described by:
R = n1a1 + n2a2 + n3a3where ni are any integers and a are known as the primi-tive vectors which lie in dierent directions and span thelattice. This discrete set of vectors must be closed undervector addition and subtraction. For any choice of posi-tion vector R, the lattice looks exactly the same.When the discrete points are atoms, ions, or polymerstrings of solid matter, the Bravais lattice concept is usedto formally dene a crystalline arrangement and its (nite)frontiers. A crystal is made up of a periodic arrangementof one or more atoms (the basis) repeated at each latticepoint. Consequently, the crystal looks the same whenviewed from any equivalent lattice point, namely thoseseparated by the translation of one unit cell (the motive).Two Bravais lattices are often considered equivalent ifthey have isomorphic symmetry groups. In this sense,there are 14 possible Bravais lattices in three-dimensionalspace. The 14 possible symmetry groups of Bravais lat-tices are 14 of the 230 space groups.
1 Bravais lattices in at most 2 di-mensions
In zero-dimensional and one-dimensional space, there isonly one type of Bravais lattice.In two-dimensional space, there are ve Bravais lattices:oblique, rectangular, centered rectangular, hexagonal(rhombic), and square.[2]
2 Bravais lattices in 3 dimensionsIn three-dimensional space, there are 14 Bravais lattices.These are obtained by combining one of the seven latticesystems (or axial systems) with one of the seven latticetypes (or lattice centerings). In general, the lattice sys-tems can be characterized by their shapes according tothe relative lengths of the cell edges (a, b, c) and the an-gles between them (, , ). The lattice types identify thelocations of the lattice points in the unit cell as follows:
|a | = |a |, = 901 2|a | = |a |, = 1201 2
a1
|a | |a |, = 901 2 |a | |a |, 901 2|a | |a |, 901 21 2 3
54
a1
a2 a2 a1
a2
a1
a2
a1
a2
The ve fundamental two-dimensional Bravais lattices: 1oblique, 2 rectangular, 3 centered rectangular, 4 hexagonal(rhombic), and 5 square. In addition to the stated conditions,the centered rectangular lattice fullls 2a2 a1 ? a1 . This or-thogonality condition leads to the rectangular pattern indicatedand implies ' 6= 90 .
Primitive (P): lattice points on the cell corners only(sometimes called simple)
Body-Centered (I): lattice points on the cell cornerswith one additional point at the center of the cell
Face-Centered (F): lattice points on the cell cornerswith one additional point at the center of each of thefaces of the cell
Base-Centered (A, B, or C): lattice points on thecell corners with one additional point at the centerof each face of one pair of parallel faces of the cell(sometimes called end-centered)
Rhombohedral (R): lattice points on the cell cornersonly where a = b = c and = = 90 (specialcase for the rhombohedral lattice system)
Not all combinations of lattice systems and lattice typesare needed to describe all of the possible lattices. If weconsider R equivalent to P, then there are in total 7 6= 42 combinations, but it can be shown that several ofthese are in fact equivalent to each other. For example,the monoclinic I lattice can be described by a monoclinicC lattice by dierent choice of crystal axes. Similarly,all A- or B-centred lattices can be described either by aC- or P-centering. This reduces the number of combina-tions to 14 conventional Bravais lattices, shown in the ta-ble below. The rhombohedral lattice is ocially assignedas type R in order to distinguish it from the hexagonal lat-
1
2 7 EXTERNAL LINKS
tice in the trigonal crystal system. However, for simplicitythis lattice is often shown as type P.The volume of the unit cell can be calculated by evaluat-ing a b c where a, b, and c are the lattice vectors. Thevolumes of the Bravais lattices are given below:Centred Unit Cells :
3 Bravais lattices in 4 dimensionsIn four dimensions, there are 64 Bravais lattices. Ofthese, 23 are primitive and 41 are centered. Ten Bravaislattices split into enantiomorphic pairs.[3]
4 See also Translational symmetry Lattice (group) classication of lattices Miller Index Translation operator (quantum mechanics)
5 References[1] Aroyo, Mois I.; Ulrich Mller; Hans Wondratschek
(2006). Historical Introduction. International Ta-bles for Crystallography (Springer) A1 (1.1): 25.doi:10.1107/97809553602060000537. Retrieved 2008-04-21.
[2] Kittel, Charles (1996) [1953]. Chapter 1. Introductionto Solid State Physics (Seventh ed.). New York: John Wi-ley & Sons. p. 10. ISBN 0-471-11181-3. Retrieved2008-04-21.
[3] Brown, Harold; Blow, Rolf; Neubser, Joachim; Won-dratschek, Hans; Zassenhaus, Hans (1978), Crystallo-graphic groups of four-dimensional space, New York:Wiley-Interscience [John Wiley & Sons], ISBN 978-0-471-03095-9, MR 0484179
6 Further reading Bravais, A. (1850). Mmoire sur les systmes for-ms par les points distribus rgulirement sur unplan ou dans l'espace. J. Ecole Polytech. 19: 1128. (English: Memoir 1, Crystallographic Societyof America, 1949.)
Hahn, Theo, ed. (2002). International Tables forCrystallography, Volume A: Space Group SymmetryA (5th ed.). Berlin, New York: Springer-Verlag.doi:10.1107/97809553602060000100. ISBN 978-0-7923-6590-7.
7 External links Catalogue of Lattices (by Nebe and Sloane) Smith, Walter Fox (2002). The Bravais LatticesSong.
38 Text and image sources, contributors, and licenses8.1 Text
Bravais lattice Source: http://en.wikipedia.org/wiki/Bravais%20lattice?oldid=661606891 Contributors: Andre Engels, Patrick, MichaelHardy, Ellywa, Tantalate, LMB, Robbot, Giftlite, Soren.harward, Mikko Paananen, DragonySixtyseven, Tomruen, Avihu, Vsmith, Zaslav,El C, .:Ajvol:., Eruantalon, SietskeEN, Hard Raspy Sci, Pfalstad, R.e.b., FlaBot, Mathbot, Chobot, DVdm, Jamesmcguigan, Prolineserver,Oysteinp, Guillom, Commander Keane bot, MalafayaBot, Dvorak729, Truelight, SashatoBot, GJaxon, Stikonas, Profjohn,WilliamDParker,Krauss, Rieman 82, Gogo Dodo, Headbomb, Escarbot, Stannered, WinBot, JamesBWatson, Tedickey, Danieljamesscott, David Eppstein,User A1, Clipjoint, Ricardogpn, Plasticup, VolkovBot, Larryisgood, AlexStamm, BotMultichill, Sibwarra, Arun 01, ClueBot, Snigbrook,Niceguyedc, DhananSekhar, Addbot, DOI bot, AndersBot, SpBot, Klicketyclack, Joule36e5, Materialscientist, Citation bot, Brane.Blokar,Mjgardes, Mnmngb, Citation bot 1, Pinethicket, LewisEE, Trappist the monk, Dinamik-bot, EmausBot, Mrsmime, Bor75, Hhhippo, Don-ner60, ClueBot NG, Neeya The Great, Xanthe-fr, Specopsgamer, Fittold27, Sanalampady, Wikifan2744, Lathamboyle, Sumeruhazra andAnonymous: 67
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Bravais lattices in at most 2 dimensionsBravais lattices in 3 dimensionsBravais lattices in 4 dimensionsSee alsoReferencesFurther readingExternal linksText and image sources, contributors, and licensesTextImagesContent license