DOC files for USER-EES

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Section_commands.html#comm)

:line

fix wall/ees command :h3

[Syntax:]

fix ID group-ID wall/ees face args ... keyword value ... :pre

ID, group-ID are documented in "fix"_fix.html command :ulb,l

one or more face/arg pairs may be appended :l

face = {xlo} or {xhi} or {ylo} or {yhi} or {zlo} or {zhi} :l

  args = coord epsilon sigma cutoff

    coord = position of wall = EDGE or constant or variable

      EDGE = current lo or hi edge of simulation box

      constant = number like 0.0 or -30.0 (distance units)

      variable = "equal-style variable"_variable.html like v_x or v_wiggle

    epsilon = strength factor for wall-particle interaction (energy or energy/distance^2 units)

      epsilon can be a variable (see below)

    sigma = size factor for wall-particle interaction (distance units)

      sigma can be a variable (see below)

    cutoff = distance from wall at which wall-particle interaction is cut off (distance units) :pre

zero or more keyword/value pairs may be appended :l

keyword = {units} or {fld} :l

  {units} value = {lattice} or {box}

    {lattice} = the wall position is defined in lattice units

    {box} = the wall position is defined in simulation box units

  {fld} value = {yes} or {no}

    {yes} = invoke the wall constraint to be compatible with implicit FLD

    {no} = invoke the wall constraint in the normal way

  {pbc} value = {yes} or {no}

    {yes} = allow periodic boundary in a wall dimension

    {no} = require non-perioidic boundaries in any wall dimension :pre

:ule

[Examples:]

fix wallhi all wall/ees xlo -1.0 1.0 1.0 2.5 units box

fix wallhi all wall/ees xhi EDGE 1.0 1.0 2.5

fix wallhi all wall/ees v_wiggle 23.2 1.0 1.0 2.5

fix zwalls all wall/ees zlo 0.0 1.0 1.0 0.858 zhi 40.0 1.0 1.0 0.858 :pre

[Description:]

Bound the simulation domain on one or more of its faces with a flat

wall that interacts with the ellipsoidal atoms in the group by generating a force

on the atom in a direction perpendicular to the wall and a torque parallel with the wall.  The energy of

wall-particle interactions E is given by:

:c,image(Eqs/fix_wall_ees.jpg)

Introduced by Babadi and Ejtehadi in "(Babadi)"_#BabadiEjtehadi. Here, {r} is the distance from the particle to the wall at

position {coord}, and Rc is the {cutoff} distance at which the 

particle and wall no longer interact. Also,  sigma_n is the distance between center of ellipsoid and the nearest point of its surface to the wall  The energy of the wall (see the image below).

:c,image(JPG/fix_wall_ees_image.jpg)

Details of using this command and specifications are the same as fix/wall command. 

The prefactor {epsilon} can be thought of as an

effective Hamaker constant with energy units for the strength of the

ellipsoid-wall interaction.  More specifically, the {epsilon} pre-factor

= 8 * pi^2 * rho_wall * rho_ellipsoid * epsilon * sigma_a * sigma_b * sigma_c, where epsilon

is the LJ parameters for the constituent LJ

particles and sigma_a, sigma_b, and sigma_c are radii of ellipsoidal particles. Rho_wall and rho_ellipsoid are the number density of the

constituent particles, in the wall and ellipsoid respectively, in units

of 1/volume.

NOTE: You must insure that r is always bigger than sigma_n for

all particles in the group, or LAMMPS will generate an error.  This

means you cannot start your simulation with particles touching the wall

position {coord} (r = sigma_n) or with particles penetrating the wall (0 =< r < sigma_n) or with particles on the wrong side of the

wall (r < 0). 

[Restrictions:] none

[Related commands:]

"fix wall"_fix_wall.html,

"pair resquared"_pair_resquared.html

[Default:]

The option defaults units = lattice, fld = no, and pbc = no.

:line

:link(BabadiEjtehadi)

[(Babadi)] Babadi and Ejtehadi, EPL, 77 (2007) 23002.

:link(Babadi)

[(Berardi)] Babadi, Ejtehadi, Everaers, J Comp Phys, 219, 770-779 (2006).

"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c

:link(lws,http://lammps.sandia.gov)

:link(ld,Manual.html)

:link(lc,Section_commands.html#comm)

:line

fix wall/region/ees command :h3

[Syntax:]

fix ID group-ID wall/region/ees region-ID epsilon sigma cutoff :pre

ID, group-ID are documented in "fix"_fix.html command

wall/region = style name of this fix command

region-ID = region whose boundary will act as wall

epsilon = strength factor for wall-particle interaction (energy or energy/distance^2 units)

sigma = size factor for wall-particle interaction (distance units)

cutoff = distance from wall at which wall-particle interaction is cut off (distance units) :ul

[Examples:]o

o

fix wall all wall/region/ees mySphere 1.0 1.0 2.5 :pre

[Description:]

Treat the surface of the geometric region defined by the {region-ID}

as a bounding wall which interacts with nearby ellipsoidal particles according to

the EES potential introduced "fix wall/ees"_fix_wall_ees.html.

Other details of this command is the same wiht "fix wall/region"_fix_wall_region.html command. 

[Restrictions:] none

[Related commands:]

"fix wall/lj93"_fix_wall.html,

"fix wall/ees"_fix_wall_ees.html

[Default:] none