Dear all,
I was quite surprised when,
during stability analysis of my wavefunction and subsequent reoptimization of it
in unrestricted space, the spin contamination was not descreased by removal of
the first-order contaminant:
SCF Done: E(RHF) =
-2277.17663511 A.U. after 1 cycles
NFock= 1 Conv=0.39D-08 -V/T= 2.0012
[..]
The wavefunction has an RHF -> UHF instability.
The two search directions are symmetric.
[..]
SCF Done: E(UHF) = -2277.19705082
a.u. after 42 cycles
Convg =
0.4967D-05
164 Fock formations.
S**2 =
2.1080
-V/T = 2.0009
<Sx>= 0.0000 <Sy>= 0.0000 <Sz>= 0.0000 <S**2>=
2.1080 S= 1.0356
<L.S>= 0.000000000000E+00
Annihilation of the first spin contaminant:
S**2 before annihilation 2.1080,
after 8.9661