2011-10-20 23:07:41 +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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2011-10-20 23:37:44 +08:00
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<H3>pair_style line/lj command
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2011-10-20 23:07:41 +08:00
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</H3>
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2011-12-01 23:35:32 +08:00
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<H3>pair_style line/lj/omp command
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</H3>
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2011-10-20 23:07:41 +08:00
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<P><B>Syntax:</B>
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</P>
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2011-10-20 23:37:44 +08:00
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<PRE>pair_style line/lj cutoff
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2011-10-20 23:07:41 +08:00
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</PRE>
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<P>cutoff = global cutoff for interactions (distance units)
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</P>
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<P><B>Examples:</B>
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</P>
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2011-10-20 23:37:44 +08:00
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<PRE>pair_style line/lj 3.0
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2011-10-20 23:07:41 +08:00
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pair_coeff * * 1.0 1.0
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pair_coeff 1 1 1.0 1.5 2.5
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</PRE>
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<P><B>Description:</B>
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</P>
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2011-10-20 23:37:44 +08:00
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<P>Style <I>line/lj</I> treats particles which are line segments as a set of
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2011-10-20 23:07:41 +08:00
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small spherical particles that tile the line segment length as
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explained below. Interactions between two line segments, each with N1
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and N2 spherical particles, are calculated as the pairwise sum of
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N1*N2 Lennard-Jones interactions. Interactions between a line segment
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with N spherical particles and a point particle are treated as the
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pairwise sum of N Lennard-Jones interactions. See the <A HREF = "pair_lj.html">pair_style
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lj/cut</A> doc page for the definition of Lennard-Jones
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interactions.
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</P>
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<P>The cutoff distance for an interaction between 2 line segments, or
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between a line segment and a point particle, is calculated from the
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position of the line segment (its center), not between pairs of
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individual spheres comprising the line segment. Thus an interaction
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is either calculated in its entirety or not at all.
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</P>
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<P>The set of non-overlapping spherical particles that represent a line
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segment, for purposes of this pair style, are generated in the
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following manner. Their size is a function of the line segment length
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and the specified sigma for that particle type. If a line segment has
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a length L and is of type I, then the number of spheres N that
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represent the segment is calculated as N = L/sigma_II, rounded up to
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an integer value. Thus if L is not evenly divisibly by sigam_II, N is
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incremented to include one extra sphere. In this case, the spheres
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must be slightly smaller than sigma_II so as not to overlap, so a new
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sigma-prime is chosen as the sphere diameter, such that L/N =
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sigma-prime. Thus the line segment interacts with other segments or
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point particles as a collection of N spheres of diameter sigma-prime,
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evenly spaced along the line segment, so as to exactly cover its
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length.
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</P>
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<P>The LJ interaction between 2 spheres on different line segments of
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types I,J is computed with an arithmetic mixing of the sigma values of
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the 2 spheres and using the specified epsilon value for I,J atom
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types. Note that because the sigma values for line segment spheres is
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computed using only sigma_II values, specific to the line segment's
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type, this means that any specified sigma_IJ values (for I != J) are
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effectively ignored.
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</P>
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2011-10-20 23:37:44 +08:00
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<P>For style <I>line/lj</I>, the following coefficients must be defined for
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each pair of atoms types via the <A HREF = "pair_coeff.html">pair_coeff</A> command
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as in the examples above, or in the data file or restart files read by
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the <A HREF = "read_data.html">read_data</A> or <A HREF = "read_restart.html">read_restart</A>
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2011-10-20 23:07:41 +08:00
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commands:
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</P>
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<UL><LI>epsilon (energy units)
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<LI>sigma (distance units)
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<LI>cutoff (distance units)
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</UL>
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<P>The last coefficient is optional. If not specified, the global cutoff
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is used.
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</P>
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<HR>
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2011-12-01 23:35:32 +08:00
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<P>Styles with a <I>cuda</I>, <I>gpu</I>, <I>omp</I>, or <I>opt</I> suffix are functionally
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the same as the corresponding style without the suffix. They have
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2011-12-14 04:35:35 +08:00
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been optimized to run faster, depending on your available hardware, as
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discussed in <A HREF = "Section_accelerate.html">Section_accelerate</A> of the
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manual. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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2011-12-01 23:35:32 +08:00
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</P>
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<P>These accelerated styles are part of the USER-CUDA, GPU, USER-OMP and OPT
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packages, respectively. They are only enabled if LAMMPS was built with
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those packages. See the <A HREF = "Section_start.html#start_3">Making LAMMPS</A>
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section for more info.
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</P>
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<P>You can specify the accelerated styles explicitly in your input script
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2012-01-28 07:39:14 +08:00
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by including their suffix, or you can use the <A HREF = "Section_start.html#start_7">-suffix command-line
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2011-12-01 23:35:32 +08:00
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switch</A> when you invoke LAMMPS, or you can
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use the <A HREF = "suffix.html">suffix</A> command in your input script.
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</P>
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2011-12-14 04:35:35 +08:00
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<P>See <A HREF = "Section_accelerate.html">Section_accelerate</A> of the manual for
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more instructions on how to use the accelerated styles effectively.
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2011-12-01 23:35:32 +08:00
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</P>
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<HR>
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2011-10-20 23:07:41 +08:00
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<P><B>Mixing, shift, table, tail correction, restart, rRESPA info</B>:
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</P>
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<P>For atom type pairs I,J and I != J, the epsilon and sigma coefficients
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and cutoff distance for all of this pair style can be mixed. The
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default mix value is <I>geometric</I>. See the "pair_modify" command for
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details.
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</P>
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<P>This pair style does not support the <A HREF = "pair_modify.html">pair_modify</A>
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shift, table, and tail options.
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</P>
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<P>This pair style does not write its information to <A HREF = "restart.html">binary restart
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files</A>.
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</P>
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<P>This pair style can only be used via the <I>pair</I> keyword of the
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<A HREF = "run_style.html">run_style respa</A> command. It does not support the
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<I>inner</I>, <I>middle</I>, <I>outer</I> keywords.
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</P>
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<HR>
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<P><B>Restrictions:</B>
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</P>
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<P>This style is part of the ASPHERE package. It is only enabled if
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LAMMPS was built with that package. See the <A HREF = "Section_start.html#2_3">Making
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LAMMPS</A> section for more info.
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</P>
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<P>Defining particles to be line segments so they participate in
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line/line or line/particle interactions requires the use the
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<A HREF = "atom_style.html">atom_style line</A> command.
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</P>
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<P><B>Related commands:</B>
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</P>
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2011-10-20 23:37:44 +08:00
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<P><A HREF = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_tri_lj.html">pair_style tri/lj</A>
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2011-10-20 23:07:41 +08:00
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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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