Cluster-in-molecule local correlation method for post-Hartree–Fock calculations of large systems

Our recent developments on cluster-in-molecule (CIM) local correlation method are reviewed in this paper. In the CIM method, the correlation energy of a large system can be approximately obtained from electron correlation calculations on a series of clusters, each of which contains a subset of occupied and virtual localised molecular orbitals in a certain region. The CIM method is a linear scaling method and its inherent parallelisation allows electron correlation calculations of very large systems to be feasible at ordinary workstations. In the illustrative applications, this approach is applied to investigate the conformational energy differences, reaction barriers, and binding energies of large systems at the levels of Moller–Plesset perturbation theory and coupled-cluster theory.