Recently, based on the local correlation ansatz of Pulay and Saebo,linear scaling Coupled-Cluster (CC) methods including a posteriori perturbative and self-consistent variants of
triples corrections were developed in our group, which
extend the application range of CC methods to large molecules.
The performance of the perturbative local triples correction L(T) is impressive, a test calculation involving about 1000 basis functions and over 300 correlated electrons takes only about 20 minutes on a state-of-the art personal computer, compared to an estimated time of {\bf 56 years} for the corresponding canonical,
i.e., non-local calculation. This reflects the reduction from
O(N^7) to O(N) scaling. In the present lecture these local CC methods are discussed with focus on the ingredients that lead to linear scaling.
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