How to get a molecular Hamiltonians in OpenFermion

Qiskit allows you to build the customized geometry of the molecule. You can also adjust the charge and multiplicity. For example, to build the Hydrogen molecule with a given equilibrium distance ED, you can write:

molecule = Molecule(geometry=[['H', [0., 0., 0.]],
                              ['H', [0., 0., ed]]],
                             charge=0, multiplicity=1)

Next, you can do this to get the Pauli operators:

qubit_op, _ = fermionic_transformation.transform(driver)

Finally this code gives you a dictionary of the weights and the decompositions of the Hamiltonian:

    decompositions = {}
    for el in qubit_op.oplist:
        ceof, pauli = [x.strip() for x in str(el).split('*')]
        decompositions[pauli] = ceof

This tutorial explains every detail. Just make sure you have the latest version of Qiskit installed. https://qiskit.org/documentation/tutorials/chemistry/01_electronic_structure.html