Time-dependent multireference coupled-cluster-based response approach for evaluating dynamic properties

A time-dependent response approach using a multireference coupled cluster wave function is presented for the calculation of frequency-dependent nonlinear properties for systems that have significant ''nondynamical'' electron correlation. The formulation is nonvariational in nature and is similar to Monkhorst's linear response approach, but has to incorporate-the time-dependent change of the cluster amplitudes and the model space coefficients, The static limit of the equation in the Fock space approach is shown to reduce to the time-independent formulation in the Fock space approach developed by one of us.