International Journal of Quantum Chemistry
Multipartitioning Møller–Plesset perturbation theory: Size‐extensivity at third order and symmetry conservation
Zoltán Rolik, Ágnes Szabados
Abstract
Abstract Multipartitioning multireference many‐body perturbation theory (Zaitevskii and Malrieu, Chem. Phys. Lett. 1995, 233, 597) is investigated with regard to symmetry and size‐extensivity. We show that the spin‐adapted formulation suffers from spatial symmetry breaking and propose a general symmetry‐conserving zero‐order Hamiltonian. We analyze size‐extensivity of various partitionings at the third order and find that extensivity holds if one‐particle quantities in the zero‐order Hamiltonian are properly chosen. In particular, third order of the spin‐adapted and general symmetry‐adapted theory prove to be extensive. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009