Local r⁴ smoothing¶
When passed to
halmd.mdsim.forces.pair_trunc, this function
transforms the potential into a C²-continuous function, and the
force into a C¹-continuous function. The degree of smoothing is controlled
with a dimensionless parameter. Before smoothing the potential is shifted to
by the force module.
The smoothing function is
with smoothing parameter and cutoff distance , and its derivative
The C²-continuous potential is
and the C¹-continuous force is
The following figure shows unmodified and C²-smooth variants of the Weeks-Chandler-Andersen potential, a purely repulsive form of the Lennard-Jones potential with cutoff .
The following figure shows the absolute value of the force.