Ensor is a python program with advanced partitioning algorithms for optimizing Quantum calculation for large molecules.
If one can divide a species of interest into fragments, employ some level of ab-initio QM to calculate the wave function, energy, and properties of each fragment, and then combine the results from the fragment calculations to predict the same properties for the whole, the possibility exists that the accuracy of the outcome can approach that which would be obtained from a full non fragmented calculation.