[Wien] question about dielectric tensor

[mlalic@oi.com.br]

Dear WIEN2k users,
I am calculating optical properties of alpha-spodumene with monoclinic
structure (space group C2/c no. 15). As expected, the dielectric tensor
is
not diagonal but have 4 non-zero components (eps_xx, eps_yy, eps_zz and
eps_xy).  My doubts refer to the question in which coordinate system
this
tensor is calculated.
Firstly I thought it was the global coordinate system (a_1, a_2, a_3),
composed of primitive vectors and defined in program by Bravais matrix.
But this system is not orthogonal, and when I diagonalize the tensor the
new eigenvectors appear to be not orthogonal also, and they should be.
Thus I concluded that the dielectric tensor should have been calculated
in
Cartesian system, but I do not know how it is defined (oriented).
In conclusion, I have 2 questions.
1.        What is the coordinate system in which the dielectric tensor
is
calculated in WIEN2k?
2.        How this system is oriented with respect to the directions of
the three
crystallographic axes a, b, c of monoclinic lattice?
The issue does not depend on concrete data in STRUCT file, thus I do not
provide them. Any help will be appreciated very much.
Sincerely,
Dr Milan Lalic
Physics Department, Federal University of Sergipe
Sao Cristovao - Brazil

--------------------------------------------------------------------------------
Na Oi Internet você ganha ou ganha. Além de acesso grátis com
qualidade, você pode ter contas ilimitadas de email com 1 giga cada uma,
suporte grátis e muito mais. Baixe grátis o Discador Oi em
http://www.oi.com.br/discador e comece a ganhar.

Agora, se o seu negócio é voar alto na internet,
assine Oi Internet Banda Larga e ganhe o modem grátis. Clique em
http://www.oi.com.br/bandalarga e aproveite essa moleza!