forked from lijiext/lammps
136 lines
5.1 KiB
Plaintext
136 lines
5.1 KiB
Plaintext
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
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:link(lws,http://lammps.sandia.gov)
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:link(ld,Manual.html)
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:link(lc,Section_commands.html#comm)
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:line
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pair_style line/lj command :h3
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pair_style line/lj/omp command :h3
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[Syntax:]
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pair_style line/lj cutoff :pre
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cutoff = global cutoff for interactions (distance units)
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[Examples:]
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pair_style line/lj 3.0
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pair_coeff * * 1.0 1.0
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pair_coeff 1 1 1.0 1.5 2.5 :pre
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[Description:]
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Style {line/lj} treats particles which are line segments as a set of
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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 "pair_style
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lj/cut"_pair_lj.html doc page for the definition of Lennard-Jones
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interactions.
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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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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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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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For style {line/lj}, the following coefficients must be defined for
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each pair of atoms types via the "pair_coeff"_pair_coeff.html 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 "read_data"_read_data.html or "read_restart"_read_restart.html
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commands:
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epsilon (energy units)
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sigma (distance units)
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cutoff (distance units) :ul
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The last coefficient is optional. If not specified, the global cutoff
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is used.
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:line
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Styles with a {cuda}, {gpu}, {omp}, or {opt} suffix are functionally
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the same as the corresponding style without the suffix. They have
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been optimized to run faster, depending on your available hardware, as
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discussed in "Section_accelerate"_Section_accelerate.html 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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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 "Making LAMMPS"_Section_start.html#start_3
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section for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the "-suffix command-line
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switch"_Section_start.html#start_7 when you invoke LAMMPS, or you can
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use the "suffix"_suffix.html command in your input script.
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See "Section_accelerate"_Section_accelerate.html of the manual for
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more instructions on how to use the accelerated styles effectively.
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:line
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[Mixing, shift, table, tail correction, restart, rRESPA info]:
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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 {geometric}. See the "pair_modify" command for
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details.
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This pair style does not support the "pair_modify"_pair_modify.html
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shift, table, and tail options.
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This pair style does not write its information to "binary restart
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files"_restart.html.
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This pair style can only be used via the {pair} keyword of the
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"run_style respa"_run_style.html command. It does not support the
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{inner}, {middle}, {outer} keywords.
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:line
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[Restrictions:]
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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 "Making
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LAMMPS"_Section_start.html#2_3 section for more info.
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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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"atom_style line"_atom_style.html command.
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[Related commands:]
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"pair_coeff"_pair_coeff.html, "pair_style tri/lj"_pair_tri_lj.html
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[Default:] none
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