Questions tagged [born-oppenheimer-approximation]

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

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4 votes
1 answer

Which programs can calculate corrections to the Born-Oppenheimer approximation?

I need to calculate the electric dipole moment of molecules like HD, in which the electric dipole moment is zero in the Born-Oppenheimer approximation (meaning that it's absolutely necessary to ...
  • 41
9 votes
2 answers

Any software that could do surface hopping?

I am trying to understand how to do the time-dependent simulation of the electron transfer, I find that the popular method is surface hopping, but I am not sure if there is any software that could ...
  • 1,843
8 votes
1 answer

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 votes
1 answer

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 ...
  • 1,560
16 votes
1 answer

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 ...
  • 1,001
29 votes
5 answers

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.
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