Questions tagged [born-oppenheimer-approximation]

For questions related to the Born-Oppenheimer approximation in materials modeling.

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How are molecular rotational states modeled within the Born Oppenheimer Approximation for polyatomic molecules?

Molecular vibrational states associated with an adiabatic electronic state within the Born-Oppenheimer Approximation are typically defined by doing the harmonic approximation for the potential at an ...
15
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1answer
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Modeling vibronic interaction beyond Born-Oppenheimer

Within Born-Oppenheimer approximation, the motion of atomic nuclei are considered as being separated from the electrons movement. Although in general this approximation is valid for a high number of ...
16
votes
1answer
88 views

When should geometry relaxation not be performed?

My understanding is that geometry relaxation (i.e. letting the nuclei follow the force gradients of the PES until they reach local minima) should usually be performed in order to get the correct ...
29
votes
5answers
477 views

What are the situations/problems where Born-Oppenheimer approximation is invalid?

We use the Born-Oppenheimer approximation in both Hartree-Fock method and DFT. What are the problems where we cannot use this approximations.