Difference between revisions of "Electron density map"
From Online Dictionary of Crystallography
m (lang) |
BrianMcMahon (talk | contribs) m (Style edits to align with printed edition) |
||
| Line 1: | Line 1: | ||
| − | <Font color="blue">Carte de densité électronique </Font>(''Fr''). <Font color="red"> | + | <Font color="blue">Carte de densité électronique </Font>(''Fr''). <Font color="red">Elektron-Dichte-Karte</Font> (''Ge''). <Font color="green">Mapa de densidad electrónica</Font> (''Sp''). <Font color="black"> Mappa di densità elettronica</Font> (''It''). <Font color="purple">電子密度図</Font> (''Ja''). |
| − | Elektron-Dichte-Karte</Font> | ||
| − | |||
== Definition == | == Definition == | ||
| − | A three-dimensional description of the electron density in a crystal structure, determined from X-ray diffraction experiments. X-rays scatter from the electron clouds of atoms in the crystal lattice; the diffracted waves from scattering planes <math>h, k, l</math> are described by [[structure factor]]s <math>\mathbf{F}_{hkl}.</math> The electron density as a function of position <math>x,y,z</math> is the Fourier transform of the structure factors: | + | A three-dimensional description of the electron density in a crystal structure, determined from X-ray diffraction experiments. X-rays scatter from the electron clouds of atoms in the crystal lattice; the diffracted waves from scattering planes <math>h, k, l</math> are described by [[structure factor]]s <math>\mathbf{F}_{hkl}.</math> The electron density as a function of position <math>x, y, z</math> is the Fourier transform of the structure factors: |
<math>\rho(xyz) = {1\over V}\sum_{hkl} F(hkl)\exp[-2\pi i(hx + ky + lz)]</math>. | <math>\rho(xyz) = {1\over V}\sum_{hkl} F(hkl)\exp[-2\pi i(hx + ky + lz)]</math>. | ||
| Line 16: | Line 14: | ||
== Units == | == Units == | ||
| − | Electron density is measured in electrons per cubic ångström, e Å<sup> | + | Electron density is measured in electrons per cubic ångström, e Å<sup>−3</sup>. |
[[Category:Structure determination]] | [[Category:Structure determination]] | ||
[[Category:X-rays]] | [[Category:X-rays]] | ||
Revision as of 13:55, 13 May 2017
Carte de densité électronique (Fr). Elektron-Dichte-Karte (Ge). Mapa de densidad electrónica (Sp). Mappa di densità elettronica (It). 電子密度図 (Ja).
Definition
A three-dimensional description of the electron density in a crystal structure, determined from X-ray diffraction experiments. X-rays scatter from the electron clouds of atoms in the crystal lattice; the diffracted waves from scattering planes [math]h, k, l[/math] are described by structure factors [math]\mathbf{F}_{hkl}.[/math] The electron density as a function of position [math]x, y, z[/math] is the Fourier transform of the structure factors:
[math]\rho(xyz) = {1\over V}\sum_{hkl} F(hkl)\exp[-2\pi i(hx + ky + lz)][/math].
The electron density map describes the contents of the unit cells averaged over the whole crystal and not the contents of a single unit cell (a distinction that is important where structural disorder is present).
Three-dimensional maps are often evaluated as parallel two-dimensional contoured sections at different heights in the unit cell.
Units
Electron density is measured in electrons per cubic ångström, e Å−3.