I have used fix wall/lj126 and fix setforce in my simulations, by
fix 1 group1 wall/lj126 zhi 10.0 1.0 1.0 1.122462048309373
fix 2 group2 wall/lj126 zlo -10.0 1.0 1.0 1.122462048309373
fix 3 group3 setforce 0 0 0
fix 4 group4 setforce 0 0 0
My question issue is about fix output.
fix output by f_1[ ], f_2[ ], f_3[ ], f_4[ ].
For fix wall/lj126, the f_1 meaning is force to keep the virtual wall? what is meaning if positive or negative values?
For fix setforce, is f_3[ ] gives the external force added to group3 to hold it rest?
From the fix wall doc page:
This fix computes a global scalar energy and a global vector of
forces, which can be accessed by various output commands. Note that
the scalar energy is the sum of interactions with all defined walls.
If you want the energy on a per-wall basis, you need to use multiple
fix wall commands. The length of the vector is equal to the number of
walls defined by the fix. Each vector value is the normal force on a
specific wall. Note that an outward force on a wall will be a negative
value for lo walls and a positive value for hi walls. The scalar and
vector values calculated by this fix are "extensive".
From the fix setforce doc page:
This fix computes a global 3-vector of forces, which can be accessed
by various output commands. This is the total force on the group of
atoms before the forces on individual atoms are changed by the fix.
The vector values calculated by this fix are "extensive".
Ask again if some part is unclear.