[Wien] Electric Field Gradient in case.scf_mini

[Daniel Kmiec]

Dear Wien2k users,

I'm trying to calculate EFG and have some questions 
concerning information about EFG in the case.scf_mini file. 
A typical entry looks like below:

         MAIN DIRECTIONS OF THE EFG   1.0000  0.2760 -0.3709                 
                                      0.4072 -0.5385  1.0000                 
                                     -0.0567  1.0000  0.6408                 
:ANG014:  ANGLE WITH OLD X-AXIS =        24.8                                
                                                                             
:ETA014:                         ASYMM. ETA =     0.56833


I found in the usersguide that, this gives the eigenvectors of 
EFG (in colums). If I'm not wrong this the axes of the "EFG cordinate 
system".
Thats why if the first column will be the x' axis (x axis in the 
EFG system) the angle with the old x axis could be calculated as 
follows:
alpha = arccos(x . x'/|x|*|x'|). However when I take 
x = (1,0,0) and x' = (1.000, 0.4072, -0.0567)
I get alpha = 22.3 instead of 24.8. 

I've checked this for several results and I have never get
exact angle shown in *.scf_mini. 

I will be appreciated if somebody could explain me how the angle 
between the axes is calculated, or if there is an error in 
my impretation.

Greetings
Daniel Kmiec

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Mag. Daniel Kmiec             http://www.ap.univie.ac.at/users/kmiec/