# Perturbation theory

BAGEL can perform various perturbation theory calculations to describe dynamical correlation, including Møller–Plesset perturbation theory (MP2), N-electron valence state perturbation theory (NEVPT2), and multireference second order perturbation theory (CASPT2). Note that the CASPT2 implementation in BAGEL is done by the automatic code generator SMITH3, and is described in the separate page.

- Møller–Plesset perturbation theory (MP2)
  - Description
  - Keywords
  - Example
  - References
- N-electron valence state perturbation theory (NEVPT2)
  - Description
  - Keywords
  - Example
  - References
- Multireference second-order perturbation theory (CASPT2)
- Relativistic multireference second-order perturbation theory (RelCASPT2)