[Wien] large energy oscillation

[Stefaan Cottenier]

>  I have just completed a calculation with Wien2K which converged to a
> reasonable result. I am happy with the result, but I noticed that the
> energy jumped up to extremely large values partway through the
> calculation, as shown below. My question is, should I worry about the
> result if this kind of jump in energy occurs, or is this a perfectly
> acceptable, normal occurence?

1) grep the :WARN label, which will tell you something more (probably bad 
integration)

2) look at some properties (:MMI, :HFF, :EFG, :RTO, ...) just before and just 
after the jump. Are they more or less similar (as far as you can tell, because 
these are non-selfconsistent values)? If they are, then you can consider these 
high energies as an 'accident de parcours'. If they are not, then you might 
have jumped into a qualitatively different solution (local minimum of the Born-
Oppenheimer surface) (your slightly larger energy after the jump compared to 
before, suggest this). In the latter case, start your calculation again from 
the original situation, with 'something' changed (for instance GAUSS instead 
of TETRA), hope you pass the problematic region smoothly this time, and change 
back to the original parameters (TETRA again) when you are near convergence, 
and converge further (it will jump here for a while, but that's normal).

Stefaan