Our approach to large scale calculations is based on fragmenting a molecular system into pieces, and performing quantum-mechanical calculations of these fragments and their pairs in the fragment molecular orbital method (FMO). After a brief summary of the methodology, some typical applications to protein-ligand complexes, chemical reactions in explicit solvent, and nanomaterials (silicon nanowires, zeolites. mesoporous silica) will be covered with some emphasis on chemical insights offered from the interaction between fragments.

D. G. Fedorov et al., Phys. Chem. Chem. Phys. 14 (2012) 7562-7577