pub fn compute_lj_force(r: f64, lj: &LjPotential) -> (f64, f64)Expand description
Compute the Lennard-Jones potential energy and scalar force magnitude at
separation r.
Returns (energy, force_magnitude) where:
energy = 4·ε·[(σ/r)^12 − (σ/r)^6]force_magnitude = 24·ε·[2(σ/r)^12 − (σ/r)^6] / r(positive = repulsive)
The caller is responsible for applying the cutoff.