What does F-Centre Mean in Chemistry

Q. What does F-centre mean in Chemistry?

Ans:- An F centre, also known as a Farbe centre (from the German Farbzentrum, where Farbe means color and zentrum means centre), is a form of crystallographic defect in which one or more unpaired electrons occupy an anionic vacancy in a crystal lattice. Because electrons in such a vacancy in a crystal lattice absorb light in the visible spectrum, a normally transparent material turns colored. The color of the compound becomes more vivid as the number of F centres increases. Color centres with F centres are a form of color centre.

Many chemicals, particularly zinc oxide, are identified using this method (yellow).

The various types of F centres

Depending on the material and radiation energy, many types of electron centres exist. An F centre is a point in a lattice where a negatively charged ion, an anion, is replaced by an electron. In certain ways, a H centre (a halogen interstitial) is the polar opposite of a F centre, thus when they collide in a crystal, they merge and cancel out both faults. This process can be induced by light, such as a laser.

Single vacancy F center: The F centre can sometimes get an additional electron, making it negatively charged and so referred to as a F centre. Similarly, when the F centre is ionized and misses an electron, it becomes a F+ centre

Complex F center: Combinations of neighboring F centres due to anion vacancies will be referred to as F2 and F3 centres, respectively, for two and three neighbors. Larger F centre clusters are undoubtedly possible, but the specifics of their behavior are unclear. 

FS centers: F centres can arise anywhere in the crystal, however if they form on the surface of an oxide crystal, they have quite different properties. In comparison to bulk F centres, electrons bound in Fs centres have lower transition energies.