SEARCH Articles Figures Tables Extended model space, perturbation Extended model space, perturbation expansion Hartree-Fock model perturbation theory Lennard-Jones models free-energy perturbation Model, perturbation calculation and diagrams Perturbation expansion from an extended model space Perturbation model Perturbation model Perturbation theory cluster model Perturbation theory, elementary models Perturbation theory, general methods for two-group model Perturbed crystal model Perturbed hard sphere model Point perturbed-cluster model Qualitative Model Perturbation Molecular Orbital Theory Symmetry adapted perturbation theory interaction potential models Taking into account small perturbations and errors of models The natural Lewis structure perturbative model