Superposition of spherical harmonics

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Discussion Overview

The discussion revolves around the representation of px and py orbitals as linear combinations of spherical harmonics, particularly in the context of quantum chemistry and the hydrogen atom. Participants explore the implications of this representation and its relevance in different potential scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how px and py orbitals can be represented as linear combinations of spherical harmonics, given that each spherical harmonic corresponds to specific quantum numbers (n, l, m).
  • Another participant provides the mathematical expressions for px and py in terms of spherical harmonics Y11 and Y1-1.
  • A mentor notes that the original post was moved to a more appropriate forum for better engagement.
  • A later reply explains that in the hydrogen atom, spherical harmonics with the same n are energetically degenerate, allowing for linear combinations to still be valid solutions of the Schrödinger equation. It is also mentioned that in molecular contexts, the potential can affect which linear combinations serve as better zeroth order solutions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial confusion regarding the representation of orbitals, but there is agreement on the mathematical validity of linear combinations in the context of the hydrogen atom. The discussion remains unresolved regarding the implications in molecular systems.

Contextual Notes

The discussion highlights the dependence on the context of hydrogen versus molecular systems and the potential perturbations that may affect the validity of certain linear combinations.

Raman Choudhary
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i am a beginner and was going through (Donald Mcquarie's "quantum chemistry" ) some discussion regarding orbitals of H-atom but i didn't get the logic behind writing px and py orbitals as linear combinations of spherical harmonics?

according to what i understood, a given spherical harmonic in itself represents a orbital depending upon n,l,m ..then how can we write a spherical harmonic as a sum of other two or spherical harmonics with same n,l.

[Mentor's note: moved from "New Member Introduction" forum to here]
[Mentor's note: title changed to be more descriptive]
 
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px = (1/sqrt2)*(Y11+ Y1-1)
py=(1/sqrt2*i)(Y11- Y1-1)
 
Welcome to PF! This forum "New Member Introductions" is for only new member introductions and some chit-chat. Real questions belong in one of our topical forums, such as our "Quantum Physics" forum:

https://www.physicsforums.com/forums/quantum-physics.62/

Please re-post your question there. More people who can actually help you hang out there, as opposed to the few people who hang out here greeting new members.
 
In hydrogen, the spherical harmonics with the same n are all energetically degenerate, so any linear combination is again a solution of the Schrödinger equation. However in molecules, the potential is perturbed and some linear combinations are better zeroth order solutions than others.
 

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