The second-order reduced density matrix method and the two-dimensional Hubbard model

Abstract The second-order reduced density matrix method (the RDM method) has performed well in determining energies and properties of atomic and molecular systems, achieving coupled-cluster singles and doubles with perturbative triples (CCSD (T)) accuracy without using the wave-function. One question that arises is how well does the RDM method perform with the same conditions that result in CCSD (T) accuracy in the strong correlation limit. The simplest and a theoretically important model for strongly correlated electronic systems is the Hubbard model. In this paper, we establish the utility of the RDM method when employing the P , Q , G , T 1 and T 2′ conditions in the two-dimensional Hubbard model case and we conduct a thorough study applying the 4 × 4 Hubbard model employing a coefficients. Within the Hubbard Hamiltonian we found that even in the intermediate setting, where U / t is between 4 and 10, the P , Q , G , T 1 and T 2′ conditions reproduced good ground state energies.