pyscf_631g_sf_adc2.py

#!/usr/bin/env python3
## vi: tabstop=4 shiftwidth=4 softtabstop=4 expandtab
import adcc
from pyscf import gto, scf

# Run SCF in pyscf
mol = gto.M(
    atom='H 0 0 0;'
         'F 0 0 2.5',
    basis='6-31G',
    unit="Bohr",
    spin=2  # =2S, ergo triplet
)
scfres = scf.UHF(mol)
scfres.conv_tol = 1e-14
scfres.conv_tol_grad = 1e-10
scfres.kernel()

# Run solver and print results
states = adcc.adc2(scfres, n_spin_flip=5, conv_tol=1e-8)
print(states.describe())

# Plot the excitation spectrum
s2s = adcc.State2States(states, initial=0)
s2s.plot_spectrum()