2006-09-22 00:22:34 +08:00
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
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<HR>
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<H3>delete_atoms command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>delete_atoms style args
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</PRE>
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<UL><LI>style = <I>group</I> or <I>region</I> or <I>overlap</I>
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<PRE> <I>group</I> args = group-ID
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<I>region</I> args = region-ID
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<I>overlap</I> args = distance type1 type2
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distance = delete atoms with neighbors within this cutoff (distance units)
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type1 = type of first atom in pair (optional)
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type2 = type of other atom in pair (optional)
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</PRE>
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>delete_atoms group edge
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delete_atoms region sphere
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delete_atoms overlap 0.3
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delete_atoms overlap 0.3 1 1
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</PRE>
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<P><B>Description:</B>
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</P>
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2006-09-29 03:55:36 +08:00
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<P>Delete the specified atoms. This command can be used to carve out
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2006-09-22 00:22:34 +08:00
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voids from a block of material or to delete created atoms that are too
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close to each other (e.g. at a grain boundary).
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</P>
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<P>For style <I>group</I>, all atoms belonging to the group are deleted.
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</P>
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<P>For style <I>region</I>, all atoms in the region volume are deleted.
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</P>
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<P>For style <I>overlap</I>, pairs of atoms within the specified cutoff
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distance are searched for, and one of the 2 atoms is deleted. If no
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atom types are specified, an atom will always be deleted if the cutoff
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criterion is met. If a single atom type is specified, then one or
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both of the atoms in the pair must be of the specified type for a
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deletion to occur. If two atom types are specified, the two atoms in
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the pair must be of the specified types for a deletion to occur. For
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a given configuration of atoms, the only guarantee is that at the end
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of the deletion operation, enough deletions will have occurred that no
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atom pairs within the cutoff (and with the specified types) will
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remain. There is no guarantee that the minimum number of atoms will
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be deleted, or that the same atoms will be deleted when running on
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different numbers of processors.
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</P>
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<P>After atoms are deleted, if the system is not molecular (no bonds),
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then atom IDs are re-assigned so that they run from 1 to the number of
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atoms in the system. This is not done for molecular systems, since it
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would foul up the bond connectivity that has already been assigned.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>The <I>overlap</I> style requires inter-processor communication to acquire
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ghost atoms and setup a neighbor list. This means that your system
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must be ready to perform a simulation before using this command (force
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fields setup, atom masses set, etc).
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</P>
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<P>If the <A HREF = "special_bonds.html">special_bonds</A> command is used with a
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setting of 0, then a pair of bonded atoms (1-2, 1-3, or 1-4) will not
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appear in the neighbor list, and thus will not be considered for
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2006-09-29 03:55:36 +08:00
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deletion by the <I>overlap</I> style. You probably don't want to be
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deleting one atom in a bonded pair anyway.
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</P>
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<P><B>Related commands:</B>
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</P>
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<P><A HREF = "create_atoms.html">create_atoms</A>
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</P>
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<P><B>Default:</B> none
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</P>
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</HTML>
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