forked from lijiext/lammps
100 lines
3.9 KiB
HTML
100 lines
3.9 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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<HR>
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<H3>pair_style hybrid command
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</H3>
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<P><B>Syntax:</B>
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</P>
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<PRE>pair_style hybrid style1 style2 ...
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</PRE>
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<UL><LI>style1,style2 = list of one or more pair styles
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</UL>
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<P><B>Examples:</B>
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</P>
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<PRE>pair_style hybrid lj/charmm/coul/long 10.0 eam
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pair_coeff 1*2 1*2 eam niu3
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pair_coeff 3 3 lj/cut/coul/cut 1.0 1.0
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pair_coeff 1*2 3 lj/cut 0.5 1.2
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</PRE>
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<P><B>Description:</B>
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</P>
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<P>The <I>hybrid</I> style enables the use of multiple pair styles in one
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simulation. A pair style can be assigned to each pair of atom types
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via the <A HREF = "pair_coeff.html">pair_coeff</A> command.
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</P>
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<P>For example, a metal on a LJ surface could be computed where the metal
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atoms interact with each other via a <I>eam</I> potential, the surface
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atoms interact with each other via a <I>lj/cut</I> potential, and the
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metal/surface interaction is also via a <I>lj/cut</I> potential.
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</P>
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<P>All pair styles that will be used must be listed in the pair_style
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hybrid command (in any order). The name of each sub-style is followed
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by its arguments, as illustrated in the example above.
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</P>
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<P>In the pair_coeff command, the first coefficient sets the pair style
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and the remaining coefficients are those appropriate to that style.
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For example, consider a simulation with 3 atom types: types 1 and 2
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are Ni atoms, type 3 are LJ atoms with charges. The following
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commands would set up a hybrid simulation:
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</P>
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<PRE>pair_style hybrid eam/alloy lj/cut/coul/cut 10.0 lj/cut 8.0
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pair_coeff * * eam/alloy nialhjea 1 1 0
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pair_coeff 3 3 lj/cut/coul/cut 1.0 1.0
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pair_coeff 1*2 3 lj/cut 0.8 1.1
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</PRE>
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<P>Note that as with any pair_style, coeffs must be defined for all I,J
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interactions. If the sub-style allows for mixing (see the
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<A HREF = "pair_modify.html">pair_modify</A> command), then I,J interactions between
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atom types which both are assigned to that sub-style do not need to be
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specified. I.e. if atom types 1 and 2 are both computed with <I>lj/cut</I>
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and coeffs for 1,1 and 2,2 interactions are specified, then coeffs for
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1,2 interactions will be generated automatically via mixing.
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</P>
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<P>If the pair_coeff command for a sub-style requires the use of * * as
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atom type arguments (e.g. the <I>eam/alloy</I> example above), then it will
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also include trailing arguments which map atom types to elements in
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the potential. These mapping arguments should be specified as 0 if
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the sub-style is not being applied to certain atom types.
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</P>
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<P>Note that you may also need to use an <A HREF = "atom_style.html">atom_style</A>
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hybrid command in your input script, if atoms in the simulation will
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have attributes from several atom styles, due to using multiple pair
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potentials.
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</P>
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<P><B>Restrictions:</B> none
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</P>
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<P>When using a long-range Coulomic solver (via the
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<A HREF = "kspace_style">kspace_style</A> command) with pair_style hybrid, one or
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more sub-styles will be of the "long" variety.
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E.g. <I>lj/cut/coul/long</I> or <I>buck/coul/long</I>. It is OK to have more
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than one sub-style with a "long" component, but you must insure that
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the short-range Coulombic cutoff used by each of these pair styles is
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consistent. Else the long-range Coulombic solve will be inconsistent.
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</P>
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<P>A pair style of <I>none</I> can be specified as an argument to pair_style
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hybrid and the corresponding pair_coeff commands, if you desire to
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turn off pairwise interactions between certain pairs of atom types.
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</P>
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<P>The hybrid style cannot include any of the <I>granular</I> styles in its
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list of styles to use.
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</P>
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<P>If you use multiple <I>coul/long</I> pair styles along with a <A HREF = "kspace_style.html">kspace
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style</A>, then you should make sure the pairwise
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Coulombic cutoff is the same for all the pair styles.
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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 = "pair_coeff.html">pair_coeff</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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