forked from lijiext/lammps
105 lines
4.4 KiB
HTML
105 lines
4.4 KiB
HTML
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<HTML>
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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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</CENTER>
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<HR>
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<H3>set command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>set ID style value
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</PRE>
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<UL><LI>ID = ID of group or atom
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<LI>style = <I>atom</I> or <I>bond</I> or <I>angle</I> or <I>dihedral</I> or <I>improper</I> or <I>charge</I> or <I>dipole</I> or <I>type</I> or <I>mol</I> or <I>x</I> or <I>y</I> or <I>z</I> or <I>vx</I> or <I>vy</I> or <I>vz</I> or <I>q</I>
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<LI>value = value to set selected atom(s) to
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>set solvent atom 2
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set edge bond 4
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set half charge 0.5
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set 100 x 0.5
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set 1492 type 3
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Set an attribute for a single atom or each atom in a group. The
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context depends on the specified <I>style</I>.
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</P>
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<P>Styles <I>atom</I>, <I>bond</I>, <I>angle</I>, <I>dihedral</I>, <I>improper</I>, <I>charge</I>, and
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<I>dipole</I> set attributes for all atoms in a group, so the specified ID
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is a group-ID string.
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</P>
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<P>Styles <I>type</I>, <I>mol</I>, <I>x</I>, <I>y</I>, <I>z</I>, <I>vx</I>, <I>vy</I>, <I>vz</I>, and <I>q</I> set the
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attribute of a single atom, so the specified ID is an atom-ID number
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(1-N).
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</P>
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<P>Since atom attributes are assigned by the <A HREF = "read_data.html">read_data</A>,
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<A HREF = "read_restart.html">read_restart</A> or <A HREF = "create_atoms.html">create_atoms</A>
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commands, this command changes those assignments. This can be useful
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for altering pairwise and molecular force interactions, since
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force-field coefficients are defined in terms of types. It can also
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be used to change the labeling of atoms when they are output in
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<A HREF = "dump.html">dump</A> files. It can also be useful for debugging purposes;
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i.e. positioning an atom at a precise location to compute subsequent
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forces or energy.
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</P>
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<P>For style <I>atom</I>, the atom type of all atoms in the group is changed
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to the specified value from 1 to ntypes. Note that ntypes must be
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within the range the simulation was initialized for. The maximum
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number of types is set by the <A HREF = "create_box.html">create_box</A> command or
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the <I>atom types</I> field in the header of the data file read by the
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<A HREF = "read_data.html">read_data</A> command.
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</P>
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<P>For style <I>bond</I>, <I>angle</I>, <I>dihedral</I>, or <I>improper</I>, the bond type
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(angle type, etc) of all bonds (angles, etc) of atoms in the group is
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changed to the specified value from 1 to nbondtypes (angletypes, etc).
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All atoms in the bond (angle, etc) must be in the group in order for
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the change to be made. The maximum number of types is set by the
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<I>bond types</I> (<I>angle types</I>, etc) field in the header of the data
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file.
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</P>
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<P>For style <I>charge</I>, the charge of each atom in the group is set to
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the specified value.
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</P>
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<P>For style <I>dipole</I>, the specified value is used as a random number
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seed. The dipole moment of each atom in the group is set to a random
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orientation with a magnitude determined by the <A HREF = "dipole.html">dipole</A>
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command setting for that atom type.
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</P>
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<P>For styles <I>type</I>, <I>mol</I>, <I>x</I>, <I>y</I>, <I>z</I>, <I>vx</I>, <I>vy</I>, <I>vz</I>, or <I>q</I>, the
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corresponding attribute of a single atom with the specified atom-ID is
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set to the specified value. E.g. the last example above, sets the
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atom-type of atom 1492 to 3. If "type" were replaced by "q", the
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charge on atom 1492 would be set to 3; if it were replaced by "mol",
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then then the molecule-ID would be set to 3. The values for x,y,z are
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in distance units, the values for vx,vy,vz are in velocity units, and
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the value for charge is in charge units, as explained by the
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<A HREF = "units.html">units</A> command.
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</P>
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<P><B>Restrictions:</B>
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</P>
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<P>This command requires inter-processor communication to coordinate the
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setting of bond types (angle types, etc). 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). This is not necessary to simply
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reset atom types.
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</P>
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<P>You cannot set the <I>mol</I> or <I>q</I> for an atom if the
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<A HREF = "atom_style.html">atom_style</A> does not have those attributes.
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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_box.html">create_box</A>, <A HREF = "create_atoms.html">create_atoms</A>,
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<A HREF = "read_data.html">read_data</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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