F centres in solids free
The free electrons trapped in the anion vacancies are called as Fcenters. Solids containing Fcentres are paramagnetic because the electrons occupying the vacant sites are unpaired.
Oct 07, 2017 This topic explains the non stoichiometric defects in solids PLAYLISTS SOLID STATE THEORY
The greater the number of Fcenters, the more intense is the color of the compound. A way of producing Fcenters is to heat a crystal in the presence of an atmosphere of the metal that constitutes the material, e. g. , NaCl heated in a metallic Na atmosphere. Na0 Na e. Na is incorporated at NaCl crystal.
It has been established that the two bands at 3. 8 and 4. 3 eV of the transient optical absorption are due to the transitions between triplet and singlet excited states of Fcentres in BeO. The polarization of excited Fcentres absorption is discussed on the basis of analysis of the splitting of singlet and triplet states in crystalline field of
The Frenkel Defect. This is a defect where an ion is removed from its lattice site, leaving a vacancy, and moved into an interstitial site. Ionic solids may have cation interstitial, as in silver halides, anion interstitials, as in BaF 2, PbCl 2, and PbBr 2, and a mixture of both cation and anion interstitials,
Solids containing Fcentres are paramagnetic because the electrons occupying the vacant sites are unpaired. 1 The free electrons trapped in the anion vacancies are called as F centers.
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