An open-shell radical: CH₃

A doublet runs spin-polarized automatically: give the molecule its spin (= 2S) and everything else is the same code path.

import jax; jax.config.update("jax_enable_x64", True)
from dftax import KS, Molecule, scf
from dftax.energy.xc import PBE, B3LYP

ch3 = Molecule.from_xyz(
    "C 0 0 0; H 0 1.079 0; H 0.934 -0.539 0; H -0.934 -0.539 0", "sto-3g", spin=1
)
for xc in (PBE(), B3LYP()):
    res = scf(KS(ch3, xc))  # spin inferred from the molecule -> alpha/beta channels
    print(f"{xc.name:6s}  E = {res.e_tot:.8f} Ha   converged={res.converged}")

PBE     E = -39.27492770 Ha   converged=True

B3LYP   E = -39.34411255 Ha   converged=True