Surface relaxation

Surface relaxation: the distance between the uppermost atomic layers (red) is changed compared to the distance inside the solid (blue); the effect is greatly exaggerated.

As surface relaxation is defined as the change in the atomic distance at or near the surface of a solid body in comparison to the regular grid arrangement within the solid.

The surface relaxation can be specified by the relative change in the distance between the atomic layers and , based on the layer distance inside the solid (the index "B" stands for English bulk , i.e. the main part): ${\displaystyle \Delta d_{ij}}$ ${\displaystyle i}$ ${\displaystyle j}$ ${\displaystyle d_{\text{B}}}$

${\displaystyle \Delta d_{ij}={\frac {d_{ij}-d_{\text{B}}}{d_{\text{B}}}}}$

Often the distance between the first two atomic layers of the solid is reduced (typical values ​​for metals , where this effect is particularly pronounced: between 0 and −15%), since attractive forces act on the atoms on the surface in a similar way like the surface tension of a liquid. In contrast, the distance between the second and third layers is increased in many cases (typical values ​​for metals: between 0 and +5%). Instead of a decrease, with some materials an increase in the distance between the first two atomic layers can also occur. ${\displaystyle d_{12}}$ ${\displaystyle \Delta d_{12}}$ ${\displaystyle d_{23}}$ ${\displaystyle \Delta d_{23}}$

The surface relaxation alone does not change the symmetry and arrangement within the surface. An additional change in the grid arrangement in the surface is called surface reconstruction.

literature

• Charles Kittel: Introduction to Solid State Physics . 14th edition. Oldenbourg Wissenschaftsverlag, Munich 2006, ISBN 3-486-57723-9 , p. 532 ( limited preview in the Google book search - original title: Introduction to Solid State Physics . Translated by Siegfried Hunklinger).
• Siegfried Hunklinger: Solid State Physics . Oldenbourg Wissenschaftsverlag, Munich 2007, ISBN 3-486-57562-7 , p. 67–68 ( limited preview in Google Book Search).
• Rainer Kassing (Ed.): Bergmann Schaefer - Textbook of Experimental Physics, Vol. 6, Solid . 2nd Edition. Walter de Gruyter, Berlin 2005, ISBN 3-11-017485-5 , p. 295 ( limited preview in Google Book search).

Individual evidence

1. ↑ Jun Wan, YL Fan, DW Gong, SG Shen, XQ Fan: Surface relaxation and stress of fcc metals: Cu, Ag, Au, Ni, Pd, Pt, Al and Pb . In: Modeling and Simulation in Materials Science and Engineering . tape 7 , no. 2 , March 1999, p. 189-206 , doi : 10.1088 / 0965-0393 / 7/2/005 .