[Wien] EFG printout in Wien2k

[Stefaan Cottenier]

> I tried to calculate the EFGs in a Ba compound which has body centered
> orthorombic space group but I am confused about the printout of the EFGs.
> Can you tell me the relation between the printout V_{11}, V_{22} and V_{33}
> and the EFGs of V_{aa}, V_{bb}, and V_{cc}, where a, b, c are the 3
> directions of the conventional lattice. I thought V_{11}=V_{aa},
> V_{22}=V_{bb} and V_{33}=V_{cc}, (assuming all off-diagonal components are
> zero), but it is not true in some cases. As a example, one Ba site with mm2
> site symmetry has  V_{11}=6, V_{22}=6 and V_{33}=-12,  but the other Ba site
> with 2/m.. site symmetry has V_{11}=6, V_{22}=-12 and V_{33}=6, however they
> should have the same EFGs, so it seems to me that the printout of the EFGs
> depends on the site symmetry of the specific site. But I don't know how the
> site symmetry determines the printout of EFG in wien2k. Does anyone has
> experience with this. Any suggestion is highly appreciated. Thanks very
> much.

You are probably looking at the following part of case.scf :

---
:EFG002:                        EFG         =    -3.89937   *10**21  V / m**2
                                V20  TOT/SRF=     1.56360     0.02547
                                V22  TOT/SRF=     2.99663    -0.02199
                                V22M TOT/SRF=     0.00000     0.00000
                                V21  TOT/SRF=     0.00000     0.00000
                                V21M TOT/SRF=     0.00000     0.00000

               2.09389    0.00000    0.00000        2.09389    0.00000  
    0.00000
               0.00000   -3.89937    0.00000        0.00000   -3.89937  
    0.00000
               0.00000    0.00000    1.80549        0.00000    0.00000  
    1.80549

          MAIN DIRECTIONS OF THE EFG   1.0000  0.0000  0.0000
                                       0.0000  1.0000  0.0000
                                       0.0000  0.0000  1.0000
:ANG002:  ANGLE WITH OLD X-AXIS =         0.0

:ETA002:                         ASYMM. ETA =     0.07396
---

The matrix at the right-hand side gives Vxx, Vyy and Vzz (or  
Vaa-Vbb-Vcc or V11-V22-V33, whatever notation you like) in the  
principal axis system. However, it does not label the axes according  
to the usual convention that abs(Vzz) should be larger than the other  
two components. That is probably your confusion. But look at :EFGxxx,  
that number is the conventional Vzz (there is a keyword :VZZxxx as  
well, which is the same quantity but only inside the muffin tin  
spheres). Also :ETAxxx is calculated according to the proper  
assignment of the axis labels.

Stefaan


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