[Wien] electric field gradient EFG

[Stefaan Cottenier]

> Concerning the electric field gradient EFG
> I found in the case .scf0 the following
> EFG is 0.72*10^21 V m^-2
>
> The questions are
> 1. what is the meaning of ASYMM. ETA in case.scf0

The EFG is a tensor of rank 2. The label :EFGxxx gives you the largest
component (Vzz or Vcc) in the principal axis system. :ETAxxx (found as well
in case.scf) is defined as (Vxx-Vyy)/Vzz, and gives you a measure of the
anisotropy in the XY-plane of the principal axis system. eta=0 means axial
symmetry about the Z-axis of the principal axis system. A good experiment
will should give 5 quantities to characterize the EFG tensor: Vzz, eta, and
e.g. the 3 Euler angles that specifiy the orientation of the principal axis
system. In a calculation, you can find these 5 pieces of information in the
EFG-section of case.scf.

> 2. In the paper of K Schwarz, C. A-Draxel and P Plaha PRB42,2051,
> 1990
> They defines Vaa, Vbb, Vcc. What is the relation between These values
> and the Vxx, Vyy and Vzz.

Most likely Vzz=Vcc etc, just different notation.

Stefaan