Question about dataset

PennyLane Help
1

Hi, my question it’s pretty simple, I want to know if its possible to change the active space when we call one of the dataset hamiltonian’s or it have a fixed structure (complete active space)?
Thanks in advance and have a nice day.

2

Hey @jnorambu!

Great question. I think this is something we’d like to have on https://pennylane.ai in the future, but for now the active space of molecules is hard-coded. This is the bit in the source code that’s relevant:

            if mol.n_orbitals <= 40:
                prog_bar.set_description("Hamiltonian Generation")
                hamiltonian, qubits = qml.qchem.molecular_hamiltonian(
                    symbols,
                    geometry,
                    charge=charge,
                    basis=basis_name,
                    method="pyscf",
                )
                active_electrons = mol.n_electrons
                active_orbitals = mol.n_orbitals
            else:
                # TODO: Add support for active orbitals in the Molecule class
                core_orbs = core_orbitals(mol)
                active_electrons = mol.n_electrons - 2 * len(core_orbs)
                active_orbitals = mol.n_orbitals - len(core_orbs)
                hamiltonian, qubits = qml.qchem.molecular_hamiltonian(
                    symbols,
                    geometry,
                    charge=charge,
                    method="pyscf",
                    active_electrons=active_electrons,
                    active_orbitals=active_orbitals,
                )

For now, you can modify this if you’d like by cloning the source code repository and setting the active space to your liking :slight_smile:. Let me know if this helps!

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