2004/12/03 | 元素间电荷迁移[Intervalence Charge Transfer]
类别(℃〖化学〗) | 评论(0) | 阅读(108) | 发表于 13:31
The excitation and subsequent transfer of an electron from a low oxidation state cation to a neighboring cation of higher oxidation state. The transfer is often excited by visible light of a certain wavelength range, producing a characteristic color. The electron then drops back down, giving off the extra energy as a small amount of heat. An example is corundum with the coupled substitution (Fe+2Ti+4).

This reaction absorbs red photons, giving sapphire its characteristic blue color. In hematite, the process absorbs all visible photons. Materials which exhibit this property retain their dark color regardless of how finely they are ground. Materials exhibiting intervalence charge transfer are also conductors.
IVCT generally displays a strong sloping spectral signature in the range 500-1000 nm. Edge-shared octahedra generally exhibit IVCT in the range 700-800 nm, while face-shared octahedra exhibit it is 800-900+ nm. Examples of systems displaying IVCT are

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In order for IVCT to occur, orbital must overlap so electrons can hop back and forth. Examples of material displaying IVCT include vivianite,
glaucophane, kyanite Al2SiO5, Prussian blue benitoite, sapphire, tourmaline.
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