MacroModel Reference Manual - ISP

Chapter 4: Operation CodesLIGB — LIGand BondsUsed chiefly for configurational searches of inorganic complexes in conjunction with the VDWBcommand.This command defines bonds to be broken, creating molecular fragments which will be movedindependently during the search. A MOLS command must be present for each fragment to bemoved. For a bidentate ligand, there will be two LIGB bonds specified for the single MOLScommand that moves the ligand; for a tridentate ligand, there will be three, and so on.This procedure allows an MCMM search to find, for example, both mer and fac isomers of anoctahedral complex with stoichiometry MA 3B 3. LIGB can also be used to extend a conformationalsearch to a configurational search; for example, by specifying bonds to chiral carbons asLIGB bonds, the R and S configurations about these carbons will be explored.arg1arg2First atom in bond to be broken (typically a metal atom)Bond(s) to be broken0 Add all bonds to arg1 to the LIGB list.>0 Add the arg1-arg2 bond to the LIGB list for arg1.