simplify FCI calculation in LUCJ tutorial

qiskit-community · Oct 5, 2023 · 5fef42b · 5fef42b
1 parent 1878c5b
commit 5fef42b
Showing 1 changed file with 9 additions and 9 deletions.
diff --git a/docs/tutorials/04-lucj.ipynb b/docs/tutorials/04-lucj.ipynb
@@ -37,21 +37,21 @@
     "hartree_fock = pyscf.scf.RHF(mol)\n",
     "hartree_fock.kernel()\n",
     "\n",
-    "# Get molecular data and molecular Hamiltonian (one- and two-body tensors)\n",
+    "# Define active space\n",
     "active_space = range(mol.nelectron // 2 - 2, mol.nelectron // 2 + 2)\n",
+    "\n",
+    "# Compute FCI energy\n",
+    "cas = pyscf.mcscf.CASCI(hartree_fock, ncas=4, nelecas=(2, 2))\n",
+    "mo = cas.sort_mo(active_space, base=0)\n",
+    "energy_fci = cas.kernel(mo)[0]\n",
+    "\n",
+    "# Get molecular data and molecular Hamiltonian (one- and two-body tensors)\n",
     "mol_data = ffsim.MolecularData.from_hartree_fock(\n",
     "    hartree_fock, active_space=active_space\n",
     ")\n",
     "norb = mol_data.norb\n",
     "nelec = mol_data.nelec\n",
-    "mol_hamiltonian = mol_data.hamiltonian\n",
-    "\n",
-    "# Compute FCI energy\n",
-    "energy_fci, _ = pyscf.fci.direct_spin1.FCI().kernel(\n",
-    "    mol_data.one_body_tensor, mol_data.two_body_tensor, norb, nelec\n",
-    ")\n",
-    "energy_fci += mol_data.core_energy\n",
-    "print(f\"FCI energy: {energy_fci}\")"
+    "mol_hamiltonian = mol_data.hamiltonian"
    ]
   },
   {