[CPMD-list] about RAMAN

[Rodolphe VUILLEUMIER]

Dear all,

The POLARIZABILITY file simply contains the polarizability tensor of the 
whole system in atomic units.

As of the file APT, it contains the atomic polar tensors for each atoms 
in the system.
The atomic polar tensor is the derivative of the forces on the atoms 
with respect to an applied external electric field. Equivalently it is, 
from a Maxwell relation, the derivative of the total dipole of the 
system with respect to the nuclei positions. It is thus an important 
ingredient of the calculation of infrared spectra intensities, for 
example used in an harmonic approximation. The trace of this tensor is 
the so-called Born charge of the considered atom.
The data are arranged in the following order (still in AU):
the APT tensor is dF_I,i/dE_j where F_I,i is the force on atom I along 
i=x,y,z and E_j is the electric field along j=x,y,z. (I,i) are the index 
of the 3Natoms lines in the APT file, one atom after the other, and j is 
the column index in the APT file.

Best regards,
Rodolphe Vuilleumier

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Rodolphe Vuilleumier
Laboratoire de Physique Theorique de Liquides
Universite Pierre et Marie Curie - Tour 16-15 - 5eme etage
4 place Jussieu - 75005 Paris - France
Tel: 33-(0)1-44-27-72-39
Fax: 33-(0)1-44-27-51-00
Email:vuilleum at lptl.jussieu.fr