2007-10-12 07:52:34 +08:00
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"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 lubricate command :h3
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[Syntax:]
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pair_style lubricate mu squeeze shear pump twist cutinner cutoff :pre
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mu = viscosity (mass/length/time units)
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squeeze = 0/1 for squeeze force off/on
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shear = 0/1 for shear force off/on
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pump = 0/1 for pump force off/on
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twist = 0/1 for twist force off/on
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cutinner = (distance units)
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cutoff = outer cutoff for interactions (distance units) :ul
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[Examples:]
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pair_style lubricate 1.5 1 1 1 0 2.3 2.4
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pair_coeff 1 1 1.8 2.0
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pair_coeff * * :pre
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[Description:]
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Style {lubricate} computes pairwise interactions between mono-disperse
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spherical particles with the formula in Appendix A of "(Ball and
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Melrose)"_#Ball which has 4 terms describing different types of
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lubrication forces between pairs of particles in a background implicit
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solvent, each of which is proportional in strength to the viscosity of
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the solvent {mu}.
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These pair-wise forces and torques are a combination of four modes of
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pair-wise interaction: squeezing, shearing, pumping, and twisting.
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Each of these modes can be turned on or off with flags in the
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pair_style command.
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Unlike most pair potentials, the two specified cutoffs (cutinner and
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cutoff) refer to the surface-to-surface separation between two
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particles, not center-to-center distance. Currently, this pair style
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can only be used for mono-disperse spheres (same radii), so that
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separation is r_ij - 2*radius, where r_ij is the center-to-center
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distance between the particles. Within the inner cutoff {cutinner},
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the forces and torques are evaluated at a separation of cutinner. The
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outer {cutoff} is the separation distance beyond which the pair-wise
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forces are zero.
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The following coefficients must be defined for each pair of atoms
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types via the "pair_coeff"_pair_coeff.html command as in the examples
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above, or in the data file or restart files read by the
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"read_data"_read_data.html or "read_restart"_read_restart.html
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commands, or by mixing as described below:
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cutinner (distance units)
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cutoff (distance units) :ul
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The two coefficients are optional. If neither is specified, the two
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cutoffs specified in the pair_style command are used. Otherwise both
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must be specified.
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:line
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[Mixing, shift, table, tail correction, per-atom energy/stress,
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restart, rRESPA info]:
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For atom type pairs I,J and I != J, the two cutoff distances for this
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pair style can be mixed. The default mix value is {geometric}. See
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the "pair_modify" command for details.
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This pair style does not support the "pair_modify"_pair_modify.html
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shift option for the energy of the pair interaction.
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The "pair_modify"_pair_modify.html table option is not relevant
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for this pair style.
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This pair style does not support the "pair_modify"_pair_modify.html
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tail option for adding long-range tail corrections to energy and
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pressure.
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This pair style does not calculate per-atom energy and stress, as used
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by the "compute epair/atom"_compute_epair_atom.html, "compute
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stress/atom"_compute_stress_atom.html, and "dump custom"_dump.html
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commands.
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This pair style writes its information to "binary restart
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files"_restart.html, so pair_style and pair_coeff commands do not need
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to be specified in an input script that reads a restart file.
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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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2007-10-12 07:57:07 +08:00
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This style is part of the "colloid" 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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2007-10-12 07:52:34 +08:00
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Because this poential computes forces and torques on particles, the
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atom style must support particles whose size is set via the
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"shape"_shape.html command. This is "atom_style"_atom_style.html
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ellipsoid and dipole. Since only spherical mono-disperse particles
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are currently allowed for pair_style lubricate, this means the 3 shape
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radii for all particle types must be the same.
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[Related commands:]
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"pair_coeff"_pair_coeff.html
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[Default:] none
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:line
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:link(Ball)
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[(Ball)] Ball and Melrose, Physica A, 247, 444-472 (1997).
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