In this thesis we explore the Coupled Cluster method in Quantum Chemistry. We have implemented an effective Coupled Cluster Singles and Doubles code. We also explore deviations from the true ground state. For this purpose we have implemented a Coupled Cluster Singles, Doubles and Triples code. Our results are in agreement with theory that Coupled Cluster converge to the ground state when including more excitations and improving the basis set. \\ Our code performance is approaching the level of the best performing software available. Further continuations of already implemented optimizations are proposed to help development of more effective Coupled Cluster code.