I am trying to compare PSI4 with couple other DFT codes and found a strange problem with SCF convergence.

I was able to simplify the non-working example to the LiF: If I take LiF and try to compute DFT energy with PBE, when the distance is sufficiently large the SCF fails. And it looks exactly like it does look for more complex cases. Sometimes similar behavior I see when try to make the geometry optimization, even near the optimal geometry.

Example (I am using python API, this is fresh 1.3 version):

```
import psi4
mol = """
Li
F 1 4.0
"""
geom = psi4.geometry(mol)
e = psi4.energy("PBE/aug-cc-pvqz",molecule=geom)
```

The cycle ends with

@DF-RKS iter 96: -105.93407344771342 3.05420e-10 1.26750e-02 DIIS

@DF-RKS iter 97: -105.93407344818426 -4.70848e-10 1.26750e-02 DIIS

@DF-RKS iter 98: -105.93407344775187 4.32394e-10 1.26750e-02 DIIS

@DF-RKS iter 99: -105.93407344819431 -4.42441e-10 1.26750e-02 DIIS

@DF-RKS iter 100: -105.93407344820115 -6.83542e-12 1.26750e-02 DIIS

which is obviously oscillation around non-ground state because somewhere soon after beginning it was around correct value

@DF-RKS iter 1: -107.00420082761590 -1.40277e-01 8.58256e-03 DIIS

@DF-RKS iter 2: -94.40386218333836 1.26003e+01 2.49009e-02 DIIS

@DF-RKS iter 3: -106.99605273796766 -1.25922e+01 8.58719e-03 DIIS

Occupation by irrep:

A1 A2 B1 B2

DOCC [ 5, 0, 1, 0 ]

@DF-RKS iter 4: -106.99127569765074 4.77704e-03 8.70503e-03 DIIS

Occupation by irrep:

A1 A2 B1 B2

DOCC [ 4, 0, 1, 1 ]

@DF-RKS iter 5: -105.54067118242492 1.45060e+00 1.68138e-02 DIIS

Occupation by irrep:

A1 A2 B1 B2

DOCC [ 5, 0, 0, 1 ]

@DF-RKS iter 6: -107.20369889781466 -1.66303e+00 8.57220e-04 DIIS

Occupation by irrep:

A1 A2 B1 B2

DOCC [ 5, 0, 1, 0 ]

@DF-RKS iter 7: -105.73636336480513 1.46734e+00 1.47178e-02 DIIS

Surprisingly, triplet state does converge. However, according to the result, the ground state should be singlet.

Could you explain, where this problem comes from and is it possible to tune some parameters to avoid this? I tried to play myself, but with no success.