The CCPT wave functions

The CCPT wave functions and energies are parametrized in terms of the cluster operator f. Therefore, before considering the expansions of the wave function and the energy, we must determine the expansion of the cluster operator in orders of the fluctuation potential... 

Let us also consider the CCPT wave function of two noninteracting systems. Since the cluster operator Tab for such systems separates, we may write the exponential operator in the following way ... 

---