[Wien] question about dielectric tensor

[Peter Blaha]

YOu can find the lattice definitions in the UG (struct file description) 
  or check SRC_nn/dirlat.f   for the definition of the lattices.

mlalic at oi.com.br schrieb:
> 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
> 
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-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
-----------------------------------------