[Pw_forum] Raman intensity from dynmat.x

[Eduardo Ariel Menendez Proupin]

Hi,
I am studying Raman spectra using the PHONON program. With dynmat I obtain a
printout of Raman intensity, e.g., for  example15 I get

#  mode   [cm-1]   [THz]    IR            Raman     depol
    1      1.45    0.0434    0.0000         0.0006    0.7500
    2      1.45    0.0434    0.0000         0.0006    0.7500
    3      1.45    0.0434    0.0000         0.0006    0.7500
    4    353.01   10.5828    5.3377        28.4633    0.7500
    5    353.01   10.5828    5.3377        28.4633    0.7500
    6    392.56   11.7686    5.3377        28.4633    0.7500

Raman intensities depend on the polarization of incoming and outgoing light
( e.g.  | \vec{e}_1 \cdot R \cdot \vec{e}_2 |^2 ), so I guess that what is
written is some sensible average , e.g., for unpolarized light or for random
rotations of the crystal axes, or both. The line of dynmat.f90 that performs
the printout is

       write (6,'(i5,f10.2,2f10.4,f15.4,f10.4)') &
            nu, freq, freq*cm1thz, infrared(nu), &
            (45.d0*alpha**2 + 7.0d0*beta2)*r1fac, &
             3.d0*beta2/(45.d0*alpha**2 + 4.0d0*beta2)

So,  "Raman" (45.d0*alpha**2 + 7.0d0*beta2)*r1fac. And alfa and beta are
functions of raman(i,j,nu), that should be the Raman tensor.

So, my doubts are,

1)  What average is the one given by (45.d0*alpha**2 + 7.0d0*beta2)  ?

2) Is it correct that raman(i,j,nu) is the Raman tensor for the phonon mode
nu ?

Thanks
-- 


Eduardo Menendez
Departamento de Fisica
Facultad de Ciencias
Universidad de Chile
Phone: (56)(2)9787439
URL: http://fisica.ciencias.uchile.cl/~emenendez
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