Exploiting the spatial locality of electron correlation within the parametrictwo-electron reduced-density-matrix method

摘要

The parametric variational two-electron reduced-density-matrix (2-RDM) method is applied tocomputing electronic correlation energies of medium-to-large molecular systems by exploiting thespatial locality of electron correlation within the framework of the cluster-in-molecule (CIM)approximation [S. Li et al., J. Comput. Chem. 23, 238 (2002); J. Chem. Phys. 125, 074109 (2006)].The 2-RDMs of individual molecular fragments within a molecule are determined, and selectedportions of these 2-RDMs are recombined to yield an accurate approximation to the correlationenergy of the entire molecule. In addition to extending CIM to the parametric 2-RDM method, we(i) suggest a more systematic selection of atomic-orbital domains than that presented in previousCIM studies and (ii) generalize the CIM method for open-shell quantum systems. The resultingmethod is tested with a series of polyacetylene molecules, water clusters, and diazobenzenederivatives in minimal and nonminimal basis sets. Calculations show that the computational cost ofthe method scales linearly with system size. We also compute hydrogen-abstraction energies for aseries of hydroxyurea derivatives. Abstraction of hydrogen from hydroxyurea is thought to be a keystep in its treatment of sickle cell anemia; the design of hydroxyurea derivatives that oxidize morerapidly is one approach to devising more effective treatments.