Hello,
I am creating a class based on the fix_wall_region class.
There is something i do not understand in this class.
After calculating the Energy contribution and resulting force of a
wall-atom interaction, the resulting scalar force is multiplied by the
vector separating the wall and the atom. (Lines 235-241 of
fix_wall_region.cpp)
ewall[0] += eng;
fx = fwall * region->contact[m].delx;
fy = fwall * region->contact[m].dely;
fz = fwall * region->contact[m].delz;
f[i][0] += fx;
f[i][1] += fy;
f[i][2] += fz;
Where region->contact[m].delx , y or z are the components of the
shortest vector between the atom and a wall (if I have correctly
understood the region class).
I understand the conversion from a scalar force to a vectorial form of
the force.
However, the scalar expression of the force should be multiplied with a
normed vector and not with a distance.
In the latter case we calculate an energy and not the force itself.
Can someone explain me why the scalar force is multiplied by a distance ?
Thanks in advance.