A direct product decomposition approach for symmetry exploitation in many‐body methods. I. Energy calculations

摘要: An analysis of the matrix contractions involved in many‐body perturbation theory and coupled‐cluster calculations leads to a convenient strategy for exploiting point group symmetry, by which number floating operations can be reduced as much factor h2, where h is order molecular group. Contrary statement literature, significant reduction computation time realized exploit symmetry not due nonlinearities equations. Rather, savings fully vectorizable direct product decomposition (DPD) method outlined here associated with individual (linear) contractions, therefore applicable both linear nonlinear models, well many body theory. In addition large made possible core memory requirements are also ≊h2. Implementation open clos...