[Wien] decomposing the ELNES or (DOS)

[Peter Blaha]

Use     x qtl

Check the UG. You can define an arbitrarely oriented coordinate system 
for each atom, so can specify in-plane and out-of-plane direction and 
corresponding decomposition.
-- 
Peter Blaha
Inst.Materials Chemistry
TU Vienna
Getreidemarkt 9
A-1060 Vienna
Austria
+43-1-5880115671


I have a problem for decomposing the ELNES (and DOS) in the crystal 
structures in monoclinic structure. This problem become more seriously 
when crystals contain some planar molecule with the different 
orientations with respect to the each other and to the lattice vectors.
I'm studying about the ELNES of an organic molecular crystal, nemely 
"Anthracene, with WIEN2k code. Anthracene unit cell contains two 
anhracene molecules (consisting of three fused benzene rings,  in a 
linear geometry) placed in a herringbone arrangement the xy plane (shown 
in the attahed figure) which are then stacked along z direction. It is 
crystallized in a monoclinic structure with the P21/a symmetry. Lattice 
parameters are

                                         a (angstrom)     b 
       c             beta (angle between a and c)
8.40
	
6.049
	
11.156
	
124˚.62΄

I have attached its structure file for you, in two view (in the z 
direction and in the xy-plane). I calculated its ELNES with a 2*2*2 
super-cell, with core hole approximation. I want to analysis the 
p21a.sdlm (attached here) file for ELNES decomposition to its ( l' , m' 
) components ( pi and sigma structures), but I have confused. Because 
the plane of the each molecule  is not normal to the a, b or c 
directions of the unit cell. Therefore, I cannot correctly determine pi 
components (that should be normal to the hydrocarbon plane) It is; also 
for sigma component . My mean is: the l'=1 , m'=0 in the case.sdlm 
cannot be attributed to the pi component and so on, Yes?? This question 
exists for DOS decomposition, too. Can anyone help me about the correct 
ELNES and DOS decomposition?