Complex sentence: Møller-Plesset perturbation theory is an implementation of perturbation theory in computational chemistry that provides a method for adding excitations to the Hartree-Fock wavefunction\\ Psi ^.
Split into simpler sentences: Møller-Plesset perturbation theory is an implementation of perturbation theory in computational chemistry. It provides a method for adding excitations to the Hartree-Fock wavefunction\\ Psi ^.