[Wien] EFG

[Stefaan Cottenier]

>     (1) I read the "step by step DFT theory" written by S. Cottenier, 
> and it said EFG is a very sensitive quantity, and *if this one converge, 
> other quantities will usually converge,too.* My question is: *Is this 
> usually true during the convergence check of RKM or kmesh, espeically 
> for magnetic system?*

Yes, it is true. However, it is not a law of nature, rather a rule of
thumb. Best is to monitor the convergence of the quantity you are
interested in. But if this is not possible in a small test cell, then
monitoring an EFG is 'usually' (again...) a safe choice.

> *    *(2) Whether it's true or not, how to calculate EFG ? I checked 
> userguide, it said 'EFG' in case.in2 will computes decomposition of 
> electric field gradient (EFG), contributions from inside spheres (the 
> total EFG is computed in lapw0), set automatically by switch -efg.  *But 
> my question is: even I used 'TOT' in case.in2, there are still :EFG*** 
> result in case.scf , so if I wanna get EFG, do I need to switch on 'EFG' 
> in case.in2 ? do i need other parameters to get the EFG result? *

The EFG is always calculated, and it's main component is printed as
:EFGxxx in case.scf. The EFG (-efg) switch in case.in2 is meant for
further analysis of the EFG. It is not useful for convergence studies.

Stefaan