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GMX-GENION(1)			    GROMACS			 GMX-GENION(1)

NAME
       gmx-genion  - Generate monoatomic ions on energetically favorable posi-
       tions

SYNOPSIS
	  gmx genion [-s [<.tpr>]] [-n [<.ndx>]] [-p [<.top>]]
		     [-o [<.gro/.g96/...>]] [-np <int>]	[-pname	<string>]
		     [-pq <int>] [-nn <int>] [-nname <string>] [-nq <int>]
		     [-rmin <real>] [-seed <int>] [-conc <real>] [-[no]neutral]

DESCRIPTION
       gmx genion randomly replaces solvent molecules  with  monoatomic	 ions.
       The  group  of solvent molecules	should be continuous and all molecules
       should have the same number of atoms.  The user should add the ion mol-
       ecules to the topology file or use the -p option	to automatically  mod-
       ify the topology.

       The  ion	 molecule type,	residue	and atom names in all force fields are
       the capitalized element names without sign. This	molecule  name	should
       be  given  with	-pname	or -nname, and the [molecules] section of your
       topology	updated	accordingly, either by hand or with -p.	Do not use  an
       atom name instead!

       Ions  which can have multiple charge states get the multiplicity	added,
       without sign, for the uncommon states only.

       For larger ions,	e.g. sulfate we	 recommended  using  gmx  insert-mole-
       cules.

OPTIONS
       Options to specify input	files:

       -s [<.tpr>] (topol.tpr)
	      Portable xdr run input file

       -n [<.ndx>] (index.ndx) (Optional)
	      Index file

       Options to specify input/output files:

       -p [<.top>] (topol.top) (Optional)
	      Topology file

       Options to specify output files:

       -o [<.gro/.g96/...>] (out.gro)
	      Structure	file: gro g96 pdb brk ent esp

       Other options:

       -np <int> (0)
	      Number of	positive ions

       -pname <string> (NA)
	      Name of the positive ion

       -pq <int> (1)
	      Charge of	the positive ion

       -nn <int> (0)
	      Number of	negative ions

       -nname <string> (CL)
	      Name of the negative ion

       -nq <int> (-1)
	      Charge of	the negative ion

       -rmin <real> (0.6)
	      Minimum distance between ions and	non-solvent

       -seed <int> (0)
	      Seed for random number generator (0 means	generate)

       -conc <real> (0)
	      Specify salt concentration (mol/liter). This will	add sufficient
	      ions to reach up to the specified	concentration as computed from
	      the volume of the	cell in	the input .tpr file. Overrides the -np
	      and -nn options.

       -[no]neutral (no)
	      This option will add enough ions to neutralize the system. These
	      ions are added on	top of those specified with -np/-nn or -conc.

KNOWN ISSUES
        If  you specify a salt	concentration existing ions are	not taken into
	 account. In effect you	therefore specify the amount  of  salt	to  be
	 added.

SEE ALSO
       gmx(1)

       More	information    about	GROMACS	   is	 available    at    <-
       http://www.gromacs.org/>.

COPYRIGHT
       2025, GROMACS development team

2025.0				 Feb 10, 2025			 GMX-GENION(1)

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