Single function with pair lubricate

Dear LAMMPS users,

I want to output the pairwise force of lubrication interaction by the command “compute pair/local”, but LAMMPS reports ERROR: Pair style does not support compute pair/local. Since this pair style does not have a sing() function.

I have two questions: 1. Why doesn’t this potential have a single function? The lubrication force and torque are pairwise. 2. Is it possible to add a single function to the pair_lubricate.cpp file? In the source file I only found the expressions for the components of the force f[i][0], f[i][1], f[i][2], without the analytical expression of the resultant force.

Thank you in advance.

Best wishes,

This is an optional feature and the authors of the pair style elected to not implement it. If the pair style computes a torque, then using the Pair::single() function makes limited sense, since there is no way to pass the torque. Also, if the pair computation requires some pre-computation or adjustment of global properties before doing the individual force/torque computations, then you cannot include those in a single() function of the pair style.

Technically, yes. Whether this is meaningful depends on the details of the pair style and that I cannot say without having a closer look and knowing more about the details of the theory that is implemented.

I don’t understand what you are asking here.