With the know-how obtained from the principal investigations of "small" molecules, we have proceeded with successively larger systems with the goal to match molecular materials used in real applications. This has been accomplished through special modelling of environmental (solvent) effects, through the development of computational-saving algorithms, and through parallelization of the computer codes. We have thereby been able to reach; the so-called Hartree-Fock limit for - up to fourth order - NLO properties for the fullerenesr; the so-called correlation lengths (or convergence lengths) for NLO in one-dimensional oligomers; and obtained properties of unpolar liquids with basically the same precision as for the gas phase.
The solvent modelling gives the macroscopic, experimentally comparable, quantity. Present projects focus on NLO in molecular crystals and 3D networks, on polar solvents through molecular dynamics simulations, and on the inclusion of relativistic effects.