title: Molecular properties from variational reduced-density-matrix theory with three-particle N-representability conditions.
abstract: Molecular ground-state energies and two-electron reduced density matrices (2-RDMs) have recently been computed without the many-electron wave function by constraining the 2-RDM to satisfy a complete set of three-positivity conditions for N representability [D. A. Mazziotti, Phys. Rev. A 74, 032501 (2006)]. Energies at both equilibrium and nonequilibrium geometries are obtained within 0.3% of the correlation energy. In this paper the authors extend this work to examine the accuracy of molecular properties, including multipole moments and components of the ground-state energy, relative to full configuration interaction (FCI). Comparisons are also made with 2-RDM methods with two-positivity conditions and two-positivity plus the generalized T1T2 conditions as well as several approximate wave function methods. Using the 2-RDM method with three-positivity conditions, the authors obtain dipole, quadrupole, and octupole moments for BeH2, BH, H2O, CO, and NH3 at equilibrium geometries that are within 0.04% of their FCI values. In addition, for the potential energy surface of N2, the 2-RDM method with three-positivity yields not only accurate total ground-state energies but also accurate expectation values of the kinetic energy operator, the electron-nuclei potential, and electron-electron repulsion.
authors.affiliation: Department of Chemistry, The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Gergely
authors.initials: G
authors.lastname: Gidofalvi
authors.forename: David A
authors.initials: DA
authors.lastname: Mazziotti
mesh_terms: D000465:Algorithms; D001704:Biopolymers / Q000737:chemistry*; D003198:Computer Simulation; D008956:Models, Chemical; D008958:Models, Molecular; D011789:Quantum Theory
chemical_list: D001704:Biopolymers