Laser spectroscopies of molecules and attempts at quantum control of chemical reactions call for a very sophisticated treatment of the nuclear as well as electronic dynamics of molecules. This means that traditional Born-Oppenheimer style,  potential-energy-surface driven descriptions of the molecular properties are inadequate.

Instead, the electrons and nuclei should be described at the same quantum-dynamical footing. The coupled-cluster methodology is ideal for this, allowing a physical picture for the various truncations and approximations needed to make calculations practical.

Currently work is underway to compute the integrals arising from the use of basis sets that are quite different from those used in traditional quantum chemical applications of the coupled cluster method.