I know a function in PSI4 computing a nuclear repulsion energy derivative located in psi4.core.Molecule.

Is there a possibility to access such function from Qiskit interface? By this "interface" I mean mostly classes Molecule, ElectronicStructureProblem and ElectronicStructureMoleculeDriver. I need this functionality to solve my problem, while I'd much prefer to stick with the general interface enabling me to use different molecule drivers (PySCF, Gaussian...), then to depend solely on PSI4. On the other hand, I don't want to write it completely by myself, if possible, to prevent redundancy in the code.


1 Answer 1


When using Qiskit Nature, to compute an ElectronicStructureProblem, you will find nuclear_repulsion_energy as a field in the ElectronicStructureResult

I will note that this value is not computed by Qiskit rather it is retrieved directly from the driver and passed along via the driver result in the ElectronicEnergy property where you will find a like-named field.

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    $\begingroup$ Thank you for your response! I found out about this one, but the only property I found is the nuclear repulsion energy itself. Is there any way to obtain its gradient "directly" from Qiskit? $\endgroup$
    – Eenoku
    Apr 4, 2022 at 20:03
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    $\begingroup$ The energy itself is the only value that the current Qiskit drivers compute/read and return in the result. $\endgroup$
    – Steve Wood
    Apr 4, 2022 at 22:07
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    $\begingroup$ Thank you very much for the info, Steve! $\endgroup$
    – Eenoku
    Apr 5, 2022 at 0:04

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