[Pw_forum] Raman and IR intensities for a metal

[Paolo Giannozzi]

On Dec 14, 2007, at 22:46 , Stefano Baroni wrote:

> According to the usual theory, they both should be zero:
> the second is given by Born effective charges (that are
> zero in metals), the former by the derivative of the inverse
> macroscopic electric constant (which is also zero). How
> can a metal be Raman or IR active?

a true metal cannot, but there cases of systems that are
considered as "metallic" and still exhibit both Raman and
IR active modes: K_3C_60, for instance

Paolo
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Paolo Giannozzi, Dept of Physics, University of Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222