forked from lijiext/lammps
90 lines
3.2 KiB
Plaintext
90 lines
3.2 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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fix wall/colloid command :h3
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[Syntax:]
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fix ID group-ID wall/colloid style coord A sigma cutoff :pre
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ID, group-ID are documented in "fix"_fix.html command
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wall/colloid = style name of this fix command
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style = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi}
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coord = position of wall (distance units)
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A = Hamaker constant for colloid-wall interactions (energy units)
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sigma = size of constituent LJ particle that integration is done over (distance units)
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cutoff = distance from wall at which wall-particle interaction is cut off (distance units) :ul
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[Examples:]
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fix wallhi all wall/colloid xhi 10.0 20.0 1.0 2.5
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fix leftwall all wall/colloid zlo 0.0 10.0 1.0 0.858 :pre
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[Description:]
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Bound the simulation domain on one of its faces with a wall of
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Lennard-Jones particles that interacts with finite-size colloidal
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particles in the group. The energy E of wall-colloid interactions is
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given by an integrated form of the "pair_style
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colloid"_pair_colloid.html potential
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:c,image(Eqs/fix_wall_colloid.jpg)
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where A is the specified Hamaker constant for the colloid-wall
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interaction, {r} is the distance from the center of the particle to
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the wall {coord}, {R} is the radius of the colloid particle, {D} is
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the distance from the surface of the colloid particle to the wall
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(r-R), sigma is the size of the constituent LJ particle integrated
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over as described below, and Rc is the cutoff value specified in the
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fix command and is the distance from the particle center to the wall.
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This colloid/wall interaction is derived by integrating over both the
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constituent LJ particles in the colloid particle and a 3d half-lattice
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of Lennard-Jones 12-6 particles in the wall.
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The wall potential is shifted so that the energy of a wall-particle
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interaction is 0.0 at the cutoff distance.
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[Restart, fix_modify, output, run start/stop, minimize info:]
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No information about this fix is written to "binary restart
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files"_restart.html.
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The "fix_modify"_fix_modify.html {energy} option is supported by this
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fix to add the energy of interaction between atoms and the wall to the
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system's potential energy as part of "thermodynamic
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output"_thermo_style.html.
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This fix computes a scalar energy and a 3-vector of forces (on the
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wall), which can be accessed by various "output
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commands"_Section_howto.html#4_15. The scalar and vector values
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calculated by this fix are "extensive", meaning they scale with the
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number of atoms in the simulation.
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No parameter of this fix can be used with the {start/stop} keywords of
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the "run"_run.html command.
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The forces due to this fix are imposed during an energy minimization,
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invoked by the "minimize"_minimize.html command.
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IMPORTANT NOTE: If you want the atom/wall interaction energy to be
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included in the total potential energy of the system (the quantity
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being minimized), you MUST enable the "fix_modify"_fix_modify.html
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{energy} option for this fix.
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[Restrictions:]
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Any dimension (xyz) that has a colloid wall must be non-periodic.
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[Related commands:]
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"fix wall/lj93"_fix_wall_lj93.html, "pair_style
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colloid"_pair_colloid.html
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[Default:] none
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