# Crystal

(Difference between revisions)
 Revision as of 15:50, 3 April 2009 (view source)← Older edit Latest revision as of 17:23, 9 November 2017 (view source)m (Tidied translations.) (7 intermediate revisions not shown) Line 1: Line 1: + بلور (''Ar''). Cristal (''Fr''). Kristall (''Ge''). Cristallo (''It''). 結晶 (''Ja''). Кристалл (''Ru''). Cristal (''Sp''). + + == Definition== == Definition== Line 7: Line 10: - Here $\textbf{a}_{i}$ and $h_{i}$ are the reciprocal lattice vectors and integer coefficients respectively and the number ''n'' is the minimum for which the positions of the peaks can be described with integer coefficient $h_{i}$. + Here $\textbf{a}_{i}^{*}$ and $h_{i}$ are the basis vectors of the reciprocal lattice and integer coefficients respectively and the number ''n'' is the minimum for which the positions of the peaks can be described with integer coefficient $h_{i}$. The conventional crystals are a special class, though very large,  for which ''n'' = 3. The conventional crystals are a special class, though very large,  for which ''n'' = 3. Line 13: Line 16: == See also == == See also == - ''Acta Cryst.'' (1992), '''A48''', 928 where  the definition of a  [http://dx.doi.org/10.1107/S0108767392008328 crystal]  appears in the '''Terms of reference''' of the IUCr commission on aperiodic crystals + *''Acta Cryst.'' (1992), A'''48''', 928 where  the definition of a  [https://doi.org/10.1107/S0108767392008328 crystal]  appears in the '''Terms of reference''' of the IUCr Commission on Aperiodic Crystals. - + - ---- + [[Category:Fundamental crystallography]] [[Category:Fundamental crystallography]]

## Latest revision as of 17:23, 9 November 2017

بلور (Ar). Cristal (Fr). Kristall (Ge). Cristallo (It). 結晶 (Ja). Кристалл (Ru). Cristal (Sp).

## Definition

A material is a crystal if it has essentially a sharp diffraction pattern. The word essentially means that most of the intensity of the diffraction is concentrated in relatively sharp Bragg peaks, besides the always present diffuse scattering. In all cases, the positions of the diffraction peaks can be expressed by

$\textbf{H}=\sum_{i=1}^nh_{i}\textbf{a}_{i}^{*}~~(n\ge 3)$

Here $\textbf{a}_{i}^{*}$ and hi are the basis vectors of the reciprocal lattice and integer coefficients respectively and the number n is the minimum for which the positions of the peaks can be described with integer coefficient hi.

The conventional crystals are a special class, though very large, for which n = 3.