KS-CC

Kohn Sham-Coupled Cluster is a coupled cluster calculation that makes use of the Kohn Sham DFT orbitals as reference, instead of the traditional HF orbitals. With this implementation the reference has already a high amount of correlation, wich makes the coupled cluster more reliable, especially for open shell systems where HF may have much more spin contamination than a GGA functional. The accuracy of the open shell calculation is said to be similar to the close shell with the classical HF reference.

KS-CC costs almost the same time as the common coupled cluster, thus making it a cheap improvement.

Programs that implement KS-CC: NWChem, Molpro