Completely renormalized EOMCCSD(T) method employing independent optimization of the cluster product terms

In this Letter, we introduce a new variant of the completely renormalized equation-of-motion method with singles, doubles, and non-iterative triples (CR-EOMCCSD(T)) that employs a novel strategy of handling the cluster product terms that naturally appears in the EOMCC-type expansion for the trial wavefunction. The new parametrization, as shown on several examples, including the N2, C2, and the ozone molecule, assures the required flexibility of the CR-EOMCCSD(T) approach especially in dealing with the challenging excited states primarily dominated by double excitations.