Several way to get wavefunction?

To get wavefunction and estimate, for instance, HOMO, LUMO, or molecular vibration
there are several way to get wavefunction, But I do not know the differnece

energy, wf = psi4.optimize(level, molecule=molecule, return_wfn=True)
psi4.optimize(level, molecule=molecule)
energy, wf =, molecule=molecule, return_wfn=True)
psi4.optimize(level, molecule=molecule)
energy, wf = psi4.frequency(level, molecule, return_wfn)

Each wf are same?
I heve to use 2) to get HOMO LUMO?
I have to use 3) to get molecular vibration information?

Best regards

1 and 2 should return the same results, including the orbital energies.
Yes, you will need to run psi4.frequency as in 3 to get the vibrational frequencies. The wfn object returned should also have all the results that 1 and 2 returned as well (such as the orbital energies).

thank you for the reply. I understood.

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