Effective Fragment Molecular Orbital Method

This chapter discusses the effective fragment molecular orbital (EFMO) method in detail, how and why it came into existence in the context of inter-molecular interactions energies calculated through effective fragment potentials (EFPs) and obtaining total energies of large molecular systems through the FMO method. The EFMO method is a hybrid between the FMO method and the EFP method. The EFMO method is based on the FMO molecular fragmentation scheme and the many-body energy expression but uses the EFP multipole-based energy expressions for long-range interactions and for evaluating the many-body polarization. The chapter also discusses the actions that were taken for the EFMO method. It further outlines the computational approach needed to calculate the EFMO energy and as it is implemented in the GAMESS program. Introduction of correlation in the EFMO methods follows that of FMO closely.