On Jan 14, 2008, at 11:50 , Miriam Marques wrote:

> I am emailing a previous unanswered question.

> Is it possible to calculate Raman intensities for "metallic systems"

> such as hcp-metals: Zn, Fe, Zr, Mg, high pressure phases of

> oxygen or high pressure phases of alkali metals using the

> ESPRESSO code?

it depends: what is the expression of Raman intensities in

"metallic systems"? The usual definition of Raman intensities

in the nonresonant limit via derivatives of the polarizabily

(this is what is calculated in Q-E) does not apply to metals.

P.

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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

Dear Miriam: you and others will forgive my ignorance, but I would 

need some further explanations. 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? Thanks - SB

On Dec 14, 2007, at 7:18 PM, Miriam Marques wrote:

>  Dear ESPRESSO users,

> 

>  I would like to know if it is possible to compute

>  Raman and Infrared intensities for a metallic system.

> 

>  Thank you very much in advance,

> 

>  Miriam.

> 

>  Dr. Miriam Marques

>  Centre for Science at Extreme Conditions.

>  The University of Edinburgh.

>  e-mail: mmarques at staffmail.ed.ac.uk

> 

> 

> --

> The University of Edinburgh is a charitable body, registered in

> Scotland, with registration number SC005336.

> 

> 

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Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center - 

Trieste

[+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype)