Unable to construct Hamiltonian

PennyLane Help Code Together
13

Hi @raghavv. The following code creates the molecular Hamiltonian for water step by step. Could you please run the code for both water and PSPCz and let me know at what stage the code breaks? Please modify the molecular info given between the dashed lines for the new molecule. Thanks!

import pennylane as qml
import openfermion
from pennylane import numpy as np
from openfermionpyscf import run_pyscf

#------------------------
symbols = ["O", "H", "H"]
x = np.array([0.0000000000,  0.0000000000,  0.1501668459,
              0.0000000000,  0.7580826553, -0.4856334229,
              0.0000000000, -0.7580826553, -0.4856334229])
mult = 1
charge = 0
basis = 'sto-3g'
core = [0, 1, 2, 3]
active = [4, 5]
filename = './water'
#------------------------

geometry = [[s, tuple(x[3 * i : 3 * i + 3])] for i, s in enumerate(symbols)]

molecule = openfermion.MolecularData(geometry, basis, mult, charge, filename=filename)

run_pyscf(molecule, run_scf=1, verbose=0)

molecule_ = openfermion.MolecularData(filename=filename)

ht = molecule_.get_molecular_hamiltonian(occupied_indices=core, active_indices=active)

hf = openfermion.transforms.get_fermion_operator(ht) # fermion hamiltonian

hq = openfermion.transforms.jordan_wigner(hf) # qubit hamiltonian

hp = qml.qchem.convert_observable(hq) # PennyLane hamiltonian

print(hp)

The output for water should be

  (-74.19370628334303) [I0]
+ (-0.15460393042639708) [Z2]
+ (-0.15460393042639708) [Z3]
+ (0.13038589407848444) [Z0]
+ (0.13038589407848444) [Z1]
+ (0.138284189609364) [Z0 Z2]
+ (0.138284189609364) [Z1 Z3]
+ (0.14767808197773874) [Z0 Z3]
+ (0.14767808197773874) [Z1 Z2]
+ (0.14966950988795605) [Z2 Z3]
+ (0.22003977334376112) [Z0 Z1]
+ (-0.00939389236837476) [Y0 Y1 X2 X3]
+ (-0.00939389236837476) [X0 X1 Y2 Y3]
+ (0.00939389236837476) [Y0 X1 X2 Y3]
+ (0.00939389236837476) [X0 Y1 Y2 X3]