High-order coupled-cluster calculations through connected octuple excitations

By exploiting a determinantal full configuration interaction (FCI) algorithm, we compute the correlation energies of molecules at any arbitrary order of coupled-cluster (CC) theory as well as high orders of configuration interaction (CI) and many-body perturbation theory (MBPT). This general-order CC program requires memory storage for three arrays of length Ndet (the number of determinants) and a modest amount of disk storage. We perform the CC calculations including all connected n-fold excitations up to n=8 for H2O, FH, and F−.