The pursuit of accurate and computationally efficient many-body tools capable of describing electron correlation is a major effort of the quantum chemistry community. The accuracy of chemical predictions strongly depends on the ability of the models to account for electron correlation. As the computational demand scales unfavourably with the size of the system, an efficient way of identifying relevant degrees of freedom may be an interesting avenue.

In this thesis, a quantum embedding approach is employed to study lattice systems, polymers, and crystals. Numerical data shows the accuracy of the quantum embedding theory when combined with high-level many-body techniques. As the size of the units that are embedded grows, a more approximate and more computationally affordable tools are called for. In this thesis, we investigate the possibility of forming such methods in the framework of coupled cluster theory.

We believe that the tools presented in this thesis could be important for accurate treatment of electron correlation in applications to realistic materials.