Nuclear repulsion energy is tough to find!

What is the expected enhancement?

It’s pretty difficult to find the nuclear repulsion energy (and probably some other interesting properties) if one doesn’t already know where to look:

# es_problem is an `ElectronicStructureProblem`
es_problem.grouped_property_transformed.get_property("ElectronicEnergy").nuclear_repulsion_energy

It would be great it the tutorials would mention where they are, e.g. the ground state solver tutorial.

(Originated from this Slack convo)

[mrossinek]

You are right! The properties tutorial should cover this but it does not specifically talk about the nuclear repulsion energy. In fact, the string-representation of the ElectronicEnergy class should be improved to also include this attribute. This requires implementing the ElectronicEnergy.__str__ method.

I do not think that this information should go into the GS tutorial since what you are suggesting is specifically designed for extracting the information before running a solver. Instead, a logical link should be made between the electronic structure tutorial and the aforementioned properties tutorial.

To summarize, fixing this issue involves the following tasks:

• implement ElectronicEnergy.__str__ which should:
  • call super().__str__()
  • append information on self.nuclear_repulsion_energy and self.reference_energy
  • append information on self.orbital_energies
  • append information on self.kinetic and self.overlap
• add a section to the Electronic Structure tutorial highlighting how to extract properties from the ElectronicStructureProblem:
  • showcase print(es_problem)
  • i.e. es_problem.get_property("some property name")
  • link to the properties tutorial for more information

[mrossinek]

A short update on this: the ElectronicStructureProblem and ElectronicEnergy are undergoing a major refactoring, of which #796 does a lot of the intended changes. This means, that my outline above is no longer up-to-date. I will make sure, that as part of this refactoring, we will significantly improve the visibility of nuclear_repulsion_energy, fixing this issue.

But I am unassigning and removing the good first issue label from here for the time being,