[Wien] Question about symmetry of detector position in TELNES calculation

[Atsushi Yamaguchi]

I have a question about setting DETECTOR POSITION for TELNES.

 

TELNES has a keyword "DETECTOR POSITION" with two parameters, theta_x and
theta_y, and I'm using this to analyze the scattering angle dependency of
EELS.

 

When the crystal has symmetric rocksalt structure, the intensity
distribution of EELS in scattering angle should be symmetric. 

But it isn't in fact in theta_x when RELATIVISTIC = 1(fully relativistic).

 

The sample is TiC(calculate C-K edge). I also set ORIENTATION SENSITIVE key
alpha = 0.00, beta = 0.00, and gamma = 0.00. 

The Q-mesh settings are NR = 50, and NT = 4.

When the detector shifts along theta_y axis (e.g. theta_x = 0.000 mrad and
theta_y = +/-1.000 mrad), the intensity of EELS are almost the same and the
distribution shows synmetry.  This seems correct.

On the other hand, the intensities at theta_x = +/-1.000 mrad (theta_y = 0
mrad) show large difference, and the distribution seems asymmetric.

 

What is the reason behind this?

 

Thanks for your help.

 

best regards

 

A. Yamaguchi

 

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