Divide-and-conquer-based symmetry adapted cluster method: Synergistic effect of subsystem fragmentation and configuration selection

In this article, we develop the symmetry adopted cluster (SAC) theory based on the divide-and-conquer (DC) method, which accomplishes the linear-scaling computational time with respect to the system size, as well as the DC-based coupled cluster (CC) method does. Although the perturbative configuration selection adopted in the SAC program significantly reduces its computational cost compared with the CC calculations, the reduction of the configurations leads to less inclusion of the total correlation energy. However, the numerical assessments confirmed that the use of the local orbitals constructed in each subsystem in DC-SAC calculations reduces the loss in total correlation energy, which provides more reliable total and relative energies than the standard SAC method.