[Wien] Quadrupole Splitting and EFG

[Stefaan Cottenier]

> I am trying to calculate the quadrupole splitting for a compound we have
> I am just curious on what EFG I need..
>
> Would is just be the :EFGxxx value,

This is the principal (or zz) component of the EFG-tensor, expressed in 
cartesian form (3x3 matrix) in its principal axis system, with the xx, 
yy and zz elements ordered such that zz is the one with the largest 
absolute value. This is the one you need. (However, mind that this does 
fix only one of the 5 degrees of freedom -- the EFG is fully specified 
only if also :ETA and the directions of the axes of the principal axis 
system with respect to the global (crystal) axis system are given.)

> the V_20 value,

This is the principal component of the spherical form of the EFG, in the 
principal axis system. It is related to :EFGxxx by a factor 2/sqrt(3) -- 
so, nothing new.

> the V_zz value,

This has the same meaning as :EFGxxx, but only calculated up to the 
muffin tin radius instead of over the entire volume of the unit cell. In 
most cases, this cover >90% of the total EFG.

You can find some EFG-related explanations and examples here: 
http://www.wien2k.at/reg_user/faq/efg2.pdf

Stefaan