Local structure: Difference between revisions

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{{Short description|Close surroundings of an atom}}

[[File:Kristallstruktur Indiumoxid.png|thumb|upright=1.5|Crystal structure of indium(III) oxide]]

The '''local structure''' is a term in [[nuclear spectroscopy]] that refers to the structure of the nearest neighbours around an atom in [[crystal]]s and [[molecule]]s. E.g. in crystals the atoms order in regularlya regular fashion on wide ranges to form even gigantic highly ordered crystals ([[Naica Mine]]). However, crystals in reality, crystals are never perfect and have impurities or defects, which means, that a foreign atom resides on a lattice site or inbetweenin between lattice sites (interstitials). These small defects and impurities cannot be seen by methods such as [[X-ray diffraction]] or [[neutron diffraction]], because these methods average in their nature of measurement over a large number of atoms and thus are insensitive to effects in local structure. Methods in nuclear spectroscopy use specific [[Atomic nucleus|nuclei]] as probe. The nucleus of an [[atom]] is about 10,000 to 150,000 times smaller than the atom itself. It experiences the [[electric field gradient|electric fields]] created by the atom's electrons that sourroundsurround the nucleus. In addition, the electric fields created by neighbouring atoms also influence the fields that the nucleus experienceexperiences. The interactions between the nucleus and these fields isare called [[hyperfine structure|hyperfine interactions]] that influence the nucleus' properties. The nucleus therefore becomes very senstivesensitive to small changes in its hyperfine structure, thatwhich can be measured by methods of nuclear spectroscopy, such as e.g. [[nuclear magnetic resonance]], [[Mössbauer spectroscopy]], and [[perturbed angular correlation]].

The '''local structure''' is a term in [[nuclear spectroscopy]] that refers to the structure of the nearest neighbours around an atom in [[crystal]]s and [[molecule]]s. E.g. in crystals the atoms order in regularly on wide ranges to form even gigantic highly ordered crystals ([[Naica Mine]]). However, crystals in reality are never perfect and have impurities or defects, which means, that a foreign atom resides on a lattice site or inbetween lattice sites (interstitials). These small defects and impurities cannot be seen by methods such as [[X-ray diffraction]] or [[neutron diffraction]], because these methods average in their nature of measurement over a large number of atoms and thus are insensitive to effects in local structure. Methods in nuclear spectroscopy use specific [[Atomic nucleus|nuclei]] as probe. The nucleus of an [[atom]] is about 10,000 to 150,000 times smaller than the atom itself. It experiences the [[electric field gradient|electric fields]] created by the atom's electrons that sourround the nucleus. In addition, the electric fields created by neighbouring atoms also influence the fields the nucleus experience. The interactions between the nucleus and these fields is called [[hyperfine structure|hyperfine interactions]] that influence the nucleus' properties. The nucleus therefore becomes very senstive to small changes in its hyperfine structure, that can be measured by methods of nuclear spectroscopy, such as e.g. [[nuclear magnetic resonance]], [[Mössbauer spectroscopy]], and [[perturbed angular correlation]].

With the same methods, the local magnetic fields in a crystal structure can also be probed and provide a magnetic local structure. This is of great importance for the understanding of defects in magnetic materials, which have wide range of applications such as modern magnetic materials or the [[giant magnetoresistance]] effect, that is used in materials in the reader heads of harddrives.

Research of the local structure of materials havehas become an important tool for the understanding of properties especially in functional materials, such as used in electronics, chips, batteries, semiconductors, or solar cells. Many of those materials are defect materials and their specific properties are controlled by defects.

==References==

{{Reflist}}

*{{cite journal|last=Kaufmann|first=Elton N|author-link=Elton N. Kaufmann|author2=Reiner J. Vianden|year=1979|title=The electric field gradient in noncubic metals|journal=Reviews of Modern Physics|volume=51|issue=1|pages=161–214|doi=10.1103/RevModPhys.51.161|bibcode=1979RvMP...51..161K}}

[[Category:Electrostatics]]

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[[Category:Quantum chemistry]]

[[Category:Electric and magnetic fields in matter]]

{{Quantum-chemistry-stub}}