[Pw_forum] Raman Intensity

[程迎春]

Dear pwscf users:
    I am trying to use the v3.2.3 to study Raman properties. In the
"INPUT_PH",
it mentions literature "M. Lazzeri and F. Mauri, Phys. Rev. Lett. 90, 036401
(2003)".
In this paper, Lazzeri computed the raman intensities form the second order
derivative
of the electronic density matrix with respect to a uniform electric field.
Moreover,
another paper "J. Sun and et. al. , Phys. Rev. B 74, 193101" discussed the
raman spectrum
via Lazzeri's method. I think this method, which has been implented int
pwscf code, is
different from the linear response method (1.S. Baroni et al. Rev. Mod.
Phys. 73, 515 (2001),
2.P. Umari and et. al. Phys. Rev. B 63, 094305), which get the raman
intensities by
polarizability tensors.
    However, I cannot understant the results of example15(AlAs)which study
the raman tensor of AlAs.
The results of Raman tensor are showed as below:
=======================================================================================================
      Raman tensor (A^2)

     atom #    1    pol.  1
     -0.201910099100E-14     -0.540966680608E-15     -0.190481225566E-15
     -0.145527656333E-14     -0.739067155197E-15     -0.517081932644E+01
     -0.556205178654E-15     -0.517081932644E+01      0.906690633696E-15
     atom #    1    pol.  2
     ...
     atom #    1    pol.  3
     ...
     atom #    2    pol.  1
     ...
     atom #    2    pol.  2
     ...
     atom #    2    pol.  3
     ...
=======================================================================================================
My questions: what does  A^2 mean? what does pol. * mean?

I have another question about the alas.dynG.
1.Do omega 1, 2, 3 stand for the acoustic mode?
2.How can I get the Raman intensities?(the last but not the least!)
 **************************************************************************
     omega( 1) =       0.043635 [THz] =       1.455501 [cm-1]
 ( -0.499893  0.000000  0.432764  0.000000 -0.250591  0.000000 )
 ( -0.499920  0.000000  0.432787  0.000000 -0.250604  0.000000 )
     omega( 2) =       0.043635 [THz] =       1.455501 [cm-1]
 (  0.189458  0.000000 -0.164016  0.000000 -0.661194  0.000000 )
 (  0.189468  0.000000 -0.164025  0.000000 -0.661229  0.000000 )
     omega( 3) =       0.043635 [THz] =       1.455501 [cm-1]
 ( -0.462802  0.000000 -0.534591  0.000000  0.000000  0.000000 )
 ( -0.462827  0.000000 -0.534620  0.000000  0.000000  0.000000 )
     omega( 4) =      10.686462 [THz] =     356.464369 [cm-1]
 ( -0.105298  0.000000  0.234486  0.000000  0.253351  0.000000 )
 (  0.272091  0.000000 -0.605913  0.000000 -0.654659  0.000000 )
     omega( 5) =      10.686462 [THz] =     356.464369 [cm-1]
 (  0.329240  0.000000  0.147848  0.000000  0.000000  0.000000 )
 ( -0.850757  0.000000 -0.382040  0.000000  0.000000  0.000000 )
     omega( 6) =      10.686462 [THz] =     356.464369 [cm-1]
 ( -0.103785  0.000000  0.231118  0.000000 -0.257044  0.000000 )
 (  0.268182  0.000000 -0.597208  0.000000  0.664201  0.000000 )
 **************************************************************************


-- 
Y. C. Cheng
Department of Phyics
Nanjing University
Nanjing 210093
P. R. China
Tel: 86-25-83592907
Email: yccheng.nju at gmail.com
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