pytc.solver.xtc_ccsd.eris_reference_energy¶

pytc.solver.xtc_ccsd.eris_reference_energy(eris)[source]¶

Return the reference energy represented by a CCSD ERI container.

RCCSD receives a Fock matrix (the reference-normal-ordered one-body coefficient) together with un-normal-ordered two-electron integrals. The scalar e_core is the compensating constant which makes this expression the requested reference energy. Keeping this small calculation outside RCCSD.get_e_hf() makes it possible to construct and validate a reference-normal-ordered ERI view without rebuilding the ERIs.