In addition to the scalability problems of the FFT used in PME, the charge spreading step involves the accumulation of overlapping sub-grids onto the charge grid, which requires careful handling in order to avoid race conditions. The analogous step in SGT involves accumulation into distinct memory addresses, greatly simplifying its parallelization. Similar to PME, the SGT forces are simple to derive due to the properties of exponentials, and the resulting forces are fully consistent with the underlying energy expression, thus preserving the microcanonical ensemble. Furthermore, the (anti)symmetric nature in which each pair of particles enters eqn. (16) ensures that Newton's third law is exactly obeyed.