### Author Topic: Basis set for Hydrogen  (Read 1729 times)

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#### jalmeida

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##### Basis set for Hydrogen
« on: August 29, 2023, 17:03 »
Dear all,

Please, what is the difference between use confined orbital for the Hydrogen atom and use directly the python class HydrogenOrbital? Are there some documentation explain better the HydrogenOrbital class (for example, the mathematical expression of the function )?

#### Anders Blom

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##### Re: Basis set for Hydrogen
« Reply #1 on: September 18, 2023, 22:38 »
ConfinedOrbitals and HydrogenOrbitals are really quite similar in shape and function. Both have compact support (they go to zero exactly at a certain cut-off radius), and they are both based on solid harmonics for the angular part. The only difference is how we determine the radial part, which in both cases is a numerical tabulated function in the end.

For a ConfinedOrbital we use the pseudo- and core density from the pseudopotential to calculate Hartree and exchange-correlation terms. For a HydrogenOrbital, there is no other density than the one for the single orbital that you are solving for, so the Hartree and exchange-correlation terms are zero and we are left with only a 1/r potential.

#### jalmeida

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##### Re: Basis set for Hydrogen
« Reply #2 on: October 4, 2023, 09:49 »
So it seems like there's no big difference in the calculation if I choose one or the other. Thank you!

#### Anders Blom

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##### Re: Basis set for Hydrogen
« Reply #3 on: October 5, 2023, 21:04 »
Not really, no, it's more a technical difference in the code, partly for historical reasons since we support pseudopotentials from several different sources.

#### jalmeida

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##### Re: Basis set for Hydrogen
« Reply #4 on: October 9, 2023, 11:00 »
All right, thank you!