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| | Greetings! I am Myrtle Shroyer. Minnesota is exactly where he's been residing for many years. Since she was 18 she's been working as a receptionist but her promotion by no means arrives. One of the issues he loves most is ice skating but he is having difficulties to discover time for it.<br><br>My web page [https://www.epapyrus.com/xe/Purchase/5258960 www.epapyrus.com] |
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| The Frenkel defect is a type of defect shown by [[crystalline solid]]s. It consists in the displacement of an atom from its lattice position to an interstitial site, creating a [[vacancy defect|vacancy]] at the original site and an [[interstitial defect]] at the new location.
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| ==Definition==
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| A '''Frenkel defect''', '''Frenkel pair''', or '''Frenkel disorder''' is a type of [[Crystallographic defects#Point defects|point defect]] in a [[crystal]] [[Crystal structure|lattice]]. The defect forms when an [[atom]] or [[cation]] leaves its place in the lattice, creating a [[Vacancy defect|vacancy]], and becomes an [[Interstitial defect|interstitial]] by lodging in a nearby location not usually occupied by an atom. Their prime mechanism of generation is by [[threshold displacement energy|particle irradiation]], as their equilibrium concentration according to the [[Boltzmann distribution]] is much smaller than the pure vacancies distribution, due to the large energy necessary for the creation of the associated interstitial atoms. The phenomenon is named after the [[Soviet Union|Soviet]] physicist [[Yakov Frenkel]], who discovered it in 1926.
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| ==Effect on Density==
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| This defect does not appreciably change the density of the solid as it involves only the migration of the ions within the crystal, thus preserving both the volume as well as mass.
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| ==Examples==
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| It is shown in ionic solids with large size difference between the anion and cation (with the cation usually smaller due to an increased [[effective nuclear charge]])
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| Some solids which display this defect - ZnS, AgCl, AgBr, AgI (due to the comparatively smaller size of Zn<sup>2+</sup> and Ag<sup>+</sup> ions)
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| To be noted : AgBr shows both Frenkel as well as [[Schottky defect]]s.
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| For example, consider a lattice formed by X and M ions. Suppose an M ion leaves the M sublattice, leaving the X sublattice unchanged. The number of interstitials formed will equal the number of vacancies formed.
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| One form of a Frenkel defect reaction in MgO with the oxygen ion leaving the lattice and going into the interstitial site written in [[Kröger–Vink notation]]:
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| <math>{Mg}^\times_{Mg}</math>+<math>{O}^\times_{O}</math>→<math>{O}^{''}_i</math>+<math>{V}^{\bullet\bullet}_{O}</math>+<math>{Mg}^\times_{Mg}</math>
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| This can be illustrated with the example of the sodium chloride crystal structure. The diagrams below are schematic two-dimensional representations.
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| [[Image:Nacllattice.svg|thumb|left|The defect-free NaCl structure]]
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| [[Image:Naclfrenkeldefect.svg|thumb|left|Two Frenkel defects within the NaCl structure]]
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| ==See also==
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| *[[DLTS]]
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| *[[Schottky defect]]
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| *[[Wigner effect]]
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| *[[Crystallographic defects]]
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| ==References==
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| {{reflist}}
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| *Kittel, Charles, [http://as.wiley.com/WileyCDA/WileyTitle/productCd-EHEP000803.html Introduction to Solid State Physics] - 8th ed. Wiley, 2005. ISBN 0-471-41526-X.
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| <!-- *[http://www.ncert.nic.in/NCERTS/textbook/textbook.htm NCERT Textbook for Standard XII (Part I)] - Reprint, December 2009, ISBN 81-7450-648-9
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| The site says links need the written permissionby NCERT. -->
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| [[Category:Crystallographic defects]]
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Greetings! I am Myrtle Shroyer. Minnesota is exactly where he's been residing for many years. Since she was 18 she's been working as a receptionist but her promotion by no means arrives. One of the issues he loves most is ice skating but he is having difficulties to discover time for it.
My web page www.epapyrus.com