MacroModel Reference Manual - ISP

Appendix D: Force-Field File FormatFixed-atom Tethering Potential (When FXAT Specified)0 None1 HarmonicD.2.2Charge ProcessingTwo new force field descriptors were added as of MacroModel 8.0:BCIBCI specifies if MacroModel should expect bond charge increments (BCI’s), bond dipoles, orneither from the force field.0 No such parameters are supplied by the force field. This also includes the SubstructureSection of the .fld file. To specify charges for force field substructures, youmust use explicit partial charges using the characters ' 8' in the first two columns(see Section D.4 on page 211).1 Expect BCI’s from the force field.2 Expect bond dipoles from force field.The default unit for BCI’s is the electron. The default unit for bond dipoles is the Debye.1 Debye = 10E-18 esu*cm = 0.208204 electron*Angstrom If units other than the defaults aresupplied by the BMFF force field server or used in the .fld file, specify the conversion factorto multiply by to get units of electrons or Debye; otherwise, specify 1.00000.BCI requires that STR specify an equation (not none).FCHFCH specifies how MacroModel should handle adding of delocalized formal charge into thecharge on a given atom to get the total fixed partial charge on that atom.0 Do not add delocalized formal charges into the charges on atoms.1 Use delocalized formal charges from the force field server. Delocalization by MacroModelof formal charges supplied by the force field server is not supported.2 Use delocalized formal charges based on the atom type formal charges in atom.typ(or .fld if DEBG 11 is specified).Conversion factors are not supported for FCH. Formal charge is always taken to be in units ofelectrons. Any conversion factor is ignored.194MacroModel 9.7 Reference Manual