[lammps-users] about fix wall/lj126


I have carefully read the codes of fix wall/lj126 of LAMMPS Jan08 . In function of void FixWallLJ126pore::post_force(int vflag), the force between wall and particle reads that fwall = r6inv*(coeff1*r6inv - coeff2) * side, that is, fwall =epsilon*[48*(sigma/r)^12-24*(sigma/r)^6]*side. But I think it is Fwall =epsilon*[48*(sigma/r)^12-24*(sigma/r)^6]* (1/r) *side. I am confused. Maybe I can’t completely understand the code.

If I code the Steele potential in a cylinder wall. Need I only modify the length of matrix wall and wall_all in FixWallLJ93::compute_scalar() and FixWallLJ93::compute_vector(int n)?
What’s the function of MPI_Allreduce(wall,wall_all,4,MPI_DOUBLE,MPI_SUM,world).

Thanks a million.


There might be a bug in the force derivative for wall 12/6. Someone
else wrote it. I'll take a look.

The MPI call sums the energy & forces across all processors.