[Wien] Dielectric function!!

[Fred Nastos]

On Sunday 05 September 2004 03:53, wien2k wrote:
> Dear everyone:
>      I'm a new wien user,When i calculate the dielectric function, the
> values for real part of dielectric function are negtive at some energy
> range,I don't know the reason,please help me!!

Because it is often negative for a range of frequencies!

See this figure for example:
http://www2.ncsu.edu/ncsu/pams/physics/aspnes_wg/martin/Berlin_vortrag/img008.JPG

Think of the Kramers-Kronig relation.  It says that the real part of the 
spectrum, in many cases, should be negative for some frequencies.

Fred

> Thanks in advance! 
> Dw Liu
>
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