Møller-Plesset Perturbation Theory (MPPT) is a post-Hartree-Fock method used in quantum chemistry to improve the accuracy of molecular electronic structure calculations. It is often used to account for electron correlation effects, which are not fully captured by the Hartree-Fock method. The theory is based on perturbation techniques where the Hamiltonian of a system is divided into a zeroth-order part and a perturbation. The most common form, MP2, includes second-order corrections to the energy.
