The resolution of identity and chain of spheres approximations for the LPNO-CCSD singles Fock term

摘要: In the present work, RIJCOSX approximation, developed earlier for accelerating SCF procedure, is applied to one of limiting factors LPNO-CCSD calculations: evaluation singles Fock term. It turns out that introduction in closed shell term causes errors below microhartree limit. If proposed procedure also combined with SCF, then a somewhat larger error occurs, but reaction energy will still remain negligible. The speedup only about 9–10 fold largest basis set applied. For case Penicillin using def2-QZVPP set, single point takes 2 day 16 h on processor leading total 2.6 as compared fully analytic calculation. Using eight processors, same calculation 14 h.