remove non-portable non-ascii blanks from fix wall/ees docs

Fix {wall/ees} bounds 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

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).

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 is:

:c,image(JPG/fix_wall_ees_image.jpg)

fix/wall command. You can also find an example in USER/ees/ under

examples/ directory.

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

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

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

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).