energy difference

[maartenvd]

pyscf:

from pyscf import gto
mol_h2o = gto.M(atom = 'N 0 0 0.2; N 0 0 0', basis = 'sto-3g')

from pyscf import scf
rhf_h2o = scf.RHF(mol_h2o)
e_h2o = rhf_h2o.kernel()

prints converged SCF energy = -52.6419222048247

fermi:

using Fermi
@molecule {
    N        0.0 0.0 0.2
    N        0.0 0.0 0.0
}

@set basis "sto-3g"

hfst = @energy rhf

prints -52.51997436116736

Can someone help me understand this energy difference?

[gustavojra]

Hi @maartenvd, sorry about this delay.

I believe that with our standard guess (GWH) we are converging on the wrong state. We are still pending a more robust guess, i.e. SAD.

If you use the bare core guess, you can get the right answer:

using Fermi
@molecule {
    N        0.0 0.0 0.2
    N        0.0 0.0 0.0
}

@set basis "sto-3g"
@set scf_guess core

hfst = @energy rhf;
hfst.energy

returns
-52.641922448130714