The Effective Fragment Potential (EFP) method is a computationally inexpensive way of modeling intermolecular interactions in non-covalently bound systems. The EFP approach can be viewed as a QM/MM scheme with no empirical parameters. Originally EFP was developed by Mark Gordon’s group,Day:1996, Gordon:2001 and was implemented in gamess.Schmidt:1993 A review of the EFP theory and applications can be found in Ref. Ghosh:2010, Gordon:2012. A related approach, also based on distributed multipoles, is called XPol; it is described in Section 12.12.
A new implementation of the EFP method based on the libefp library by Dr. Ilya Kaliman (see https://libefp.github.io) has been added to Q-Chem.Kaliman:2013, Kaliman:2015 The new EFP module is called EFPMAN2. EFPMAN2 can run calculations in parallel on shared memory multi-core computers and clusters of computers. EFPMAN2 is interfaced with the CCMAN and CCMAN2 modules to allow coupled cluster and EOM-CC calculations with EFP. CIS and TDDFT calculations with EFP are also available.