[molpro-user] Helium UHF energy

[Gerald Knizia]

On Thursday 01 October 2009 19:24, Lorenzo Lodi wrote:
> I was playing around with Molpro and I noticed that, for the helium
> atom, I obtain the same energy for RHF and UHF (I think UHF should be
> lower). 

For closed-shell systems near equilibrium, RHF and UHF are supposed to give 
the same energy values. If they don't (i.e., if you're getting 
symmetry-broken UHF solutions), it usually is an indication that both are bad 
and that you're dealing with a multi-reference case.
-- 
Gerald Knizia