TypeError: molecular_hamiltonian() got an unexpected keyword argument 'package'

PennyLane Help
1

Hello! I recently started with quantum computing. I am going to run pennylane with psi4. The following packages are installed: psi4, pennylane, openfermion, openfermionpsi4.
I got an error for a simple below code when I want to invoke psi4 package:

import pennylane as qml
from pennylane import qchem
from pennylane import numpy as np
import psi4
from openfermion.chem import MolecularData
from openfermionpsi4 import run_psi4
import tensorflow as tf

import time
start_time = time.time()

ang_coords = np.array([1.360247,0.000234,0.0903980,
1.790936,-0.799199,-0.262393,
1.790957,0.797996,-0.2661300])

symbols = [“O”,“H”,“H”]
geometry = np.array(ang_coords, requires_grad=True)

import tensorflow as tf
tensor = tf.constant(geometry)
geometry_arr = tensor.numpy()

H, qubits = qchem.molecular_hamiltonian(
symbols,
geometry_arr,
active_electrons=2,
active_orbitals=3, package=“psi4”)

singles, doubles = qchem.excitations(active_electrons, qubits)
print(qubits)

Error:
TypeError: molecular_hamiltonian() got an unexpected keyword argument ‘package’

Any comments would be appreciated.
Thanks

2

Hi @f.molani and welcome to the forum!

Please note that this keyword has been deprecated and removed. We now use method to identify the quantum chemistry method used to solve the mean field electronic structure problem. The available options are method="dhf" to specify the built-in differentiable Hartree-Fock solver, or method="pyscf" to use the OpenFermion-PySCF plugin. For more information please see here. Please also note that we do not support psi4 directly, but you can use any package to solve the electronic structure problem and then use this demo to build your Hamiltonian using PennyLane.

Please let us know if you have any other questions.