MacroModel Reference Manual - ISP

Chapter 4: Operation CodesTable 4.1. ASCII to decimal number conversion table. (Continued)Char Num Char Num Char Num Char Num Char Num: 58 N 78 b 98 v 118; 59 O 79 c 99 w 119< 60 P 80 d 100 x 120EXNB — use EXtended noNBonded cutoffsDespite its name, this command can be used to specify short as well as long cutoffs.Extended cutoff distances are, by default, 8 Å in vdW, 20 Å in charge/charge electrostatics.Standard defaults in the absence of this command are 7 Å for vdW and 12 Å for charge/chargeelectrostatics. Other cutoffs may be selected by adding values for arg5-8. Calculations dealingwith ions should use the EXNB option.Large distance values for cutoffs generally slow calculations but often make convergencesmoother. Occasional problems with energies and gradients which appear to increase uponrepeated minimizations may usually be solved by using long van der Waals and electrostaticcutoff distances. The native MM2/MM3 and MMFF programs use complete pair lists (nocutoffs) for van der Waals and electrostatic interactions.arg 1Long-range derivative update intervalIterations (timesteps) per recalculation of long range (>5 Å) nonbonded derivatives(Default: 10), except when one of the following special values is used:1 The constant long-range derivative option is turned off, and the entire pair list isused in the evaluation of nonbonded derivatives.2 All nonbonded pairs are put on the pair list, and the pair list is never updated. Longrangederivatives are used.3 Like a combination of 1 and 2: all nonbonded pairs are put on the pair list, the pairlist is never updated, and the entire pair list is used in each evaluation of nonbondedderivatives.arg 2arg5Long-range derivative distance cutoffDistance (integer, in angstroms) for distinction between close- and long-range nonbondedinteractions, used in constant derivative option. Default value is 5. Longerdistances give more accurate derivatives but slow the calculation.van der Waals cutoffMacroModel 9.7 Reference Manual 37