forked from lijiext/lammps
90 lines
3.6 KiB
HTML
90 lines
3.6 KiB
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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>atom_style command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>atom_style style args
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</PRE>
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<UL><LI>style = <I>angle</I> or <I>atomic</I> or <I>bond</I> or <I>charge</I> or <I>dipole</I> or <I>dpd</I> or <I>full</I> or <I>granular</I> or <I>molecular</I> or <I>hybrid</I>
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</UL>
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<PRE> args = none for any style except <I>hybrid</I>
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<I>hybrid</I> args = list of one or more styles
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</PRE>
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<P><B>Examples:</B>
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</P>
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<PRE>atom_style bond
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atom_style full
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atom_style hybrid charge bond
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>Define what style of atoms to use in a simulation. This determines
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what attributes are associated with the atoms. This command must be
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used before a simulation is setup via a <A HREF = "read_data.html">read_data</A>,
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<A HREF = "read_restart.html">read_restart</A>, or <A HREF = "create_box.html">create_box</A>
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command.
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</P>
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<P>Once a style is assigned, it cannot be changed, so use a style general
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enough to encompass all attributes. E.g. with style <I>bond</I>, angular
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terms cannot be used or added later to the model. It is OK to use a
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style more general than needed, though it may be slightly inefficient.
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</P>
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<P>The choice of style affects what quantities are stored by each atom,
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what quantities are communicated between processors to enable forces
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to be computed, and what quantities are listed in the data file read
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by the <A HREF = "read_data.html">read_data</A> command.
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</P>
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<P>These are the attributes of each style. All styles store coordinates,
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velocities, atom IDs and types.
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</P>
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<UL><LI><I>angle</I> = bonds and angles - e.g. bead-spring polymers with stiffness
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<LI><I>atomic</I> = only the default values
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<LI><I>bond</I> = bonds - e.g. bead-spring polymers
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<LI><I>charge</I> = charge
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<LI><I>dipole</I> = charge + dipole moments
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<LI><I>dpd</I> = default values, also communicates velocities
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<LI><I>molecular</I> = bonds, angles, dihedrals, impropers - e.g. all-atom polymers
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<LI><I>full</I> = molecular + charge - e.g. biomolecules, charged polymers
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<LI><I>granular</I> = granular material with rotational properties
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</UL>
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<P>Typical simulations with a single pair potential will use only one of
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these styles. For cases where multiple pair potentials will be used
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(see the <A HREF = "pair_style.html">pair_style</A> <I>hybrid</I> command), it may be
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necessary to use multiple atom styles. Another example is doing a DPD
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simulations with bonds or angles. In these cases the <I>hybrid</I> style
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can be used to list multiple atom styles. Atoms will then store and
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communicate the union of all quantities implied by the individual
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styles.
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</P>
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<P>LAMMPS can be extended with new atom styles; see <A HREF = "Section_modify.html">this
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section</A>.
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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 cannot be used after the simulation box is defined by a
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<A HREF = "read_data.html">read_data</A> or <A HREF = "create_box.html">create_box</A> command.
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</P>
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<P>The <I>angle</I>, <I>bond</I>, <I>full</I>, and <I>molecular</I> styles are part of the
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"molecular" package. The <I>granular</I> style is part of the "granular"
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package. The <I>dpd</I> style is part of the "dpd" package. They are only
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enabled if LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_2">Making
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LAMMPS</A> section for more info.
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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 = "read_data.html">read_data</A>, <A HREF = "pair_style.html">pair_style</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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