Theoretical development of the fragment molecular orbital (FMO) method

The fragment molecular orbital (FMO) method has been introduced in detail, with the emphasis on physical ideas constituting the foundation of the method. The recent theoretical development incorporating electron correlation at various levels has been covered. The means to compute the amount of interactions between fragments, including polarization and charge transfer, have been elucidated, with practical applications to a model system and a biological problem. The absolute and relative accuracy of the FMO total energies have been scrupulously established by comparison with ab initio methods. The practical issues of applying the method to real-life problems have been dealt with, including fragmentation, the choice of basis sets and parallelization. It is hoped that this very detailed description enables a general reader to apply the method to practical problems, as well as to extract a physical picture of the interactions therein.