Symmetry groups of molecule - Hamiltonian

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Discussion Overview

The discussion revolves around the relationship between molecular symmetry and the Hamiltonian of molecules, specifically whether the Hamiltonian commutes with all symmetry elements of a molecule's point symmetry group. The scope includes theoretical considerations and potential references for demonstration.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant asks if the Hamiltonian of a molecule belonging to a specific point symmetry group commutes with all symmetry elements of that group.
  • Several participants affirmatively respond "yes" to the initial question.
  • Another participant requests references or demonstrations for the claim about the Hamiltonian and symmetry elements.
  • A participant suggests that the answer is largely by definition, noting the indistinguishability of atoms with the same number of protons and neutrons and the implications for second-quantized formulations.
  • It is mentioned that in practice, first-quantized formulations are used, and molecular force fields are set up to enforce symmetry through identical coefficients on terms differing only by permutation.
  • One participant expresses a suspicion that the answer is "yes," indicating a level of uncertainty and seeking further confirmation or demonstration.

Areas of Agreement / Disagreement

While there is agreement among some participants that the Hamiltonian commutes with symmetry elements, the discussion remains unresolved regarding the provision of references or demonstrations to support this claim.

Contextual Notes

Participants express uncertainty regarding the availability of references and the definitions involved in the discussion, particularly concerning the indistinguishability of particles and the formulations used.

Konte
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Hello everybody,

As I mentioned in the title, it is about molecular symmetry and its Hamiltonian.
My question is simple:
For any molecule that belong to a precise point symmetry group. Is the Hamiltonian of this molecule commute with all the symmetry element of its point symmetry group?

Thanks.
Konte
 
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A. Neumaier said:
Yes.
Thank you for your answer.
Could you please indicate how to demonstrate this (any link or book?)
 
Konte said:
Thank you for your answer.
Could you please indicate how to demonstrate this (any link or book?)
I don't know of a reference. This is more or less by definition, because atoms with the same number of protons and neutrons are indistinguishable. If you use a second-quantized formulation, you cannot create Hamiltonians where this fails.

In practice one uses first-quantized formulations only and enforces this through how the molecular force field is set up - by imposing identical coefficients on terms that differ only by a permutation.
 
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A. Neumaier said:
I don't know of a reference. This is more or less by definition, because atoms with the same number of protons and neutrons are indistinguishable. If you use a second-quantized formulation, you cannot create Hamiltonians where this fails.

In practice one uses first-quantized formulations only and enforces this through how the molecular force field is set up.

Many thanks anyway. In fact, I suspect that the answer is "yes" , so you reassure me largely.
I turn to somebody who can indicate any demonstration if possible please.

Thanks
 

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