The last property we analyzed was the dependence on the direct space cutoff distance. We used the same 197,159-atom salt water box used for studying the dependence of the target error threshold above. Similar to the previous sections, target error thresholds of 10 -4 and 10 -8 were used for determining the runtime and accuracy, respectively. Similar to both FMM and PME, there is an optimal direct space cutoff distance for GLST (Fig. ). The optimal cutoff arises from the balancing of the short-range and long-range components. Above the optimal cutoff distance, calculation of short-range pairwise interactions dominates. On the other hand, below the optimal cutoff distance, the long-range term dominates as a result of a larger number of cubature nodes needed to achieve the target error threshold for smaller distance ranges. As evident from Fig. , choosing the correct cutoff is essential for optimal performance, choosing an inappropriate cutoff can result in almost a 10× performance penalty. Similar to the previous sections, the accuracy is only slightly affected by the direct space cutoff distance (Fig. ). While the RMSE does slightly increase for smaller cutoff distances, the increase in error stays on the order of 10 -8 . Analyzing the histograms of the per-atom error in energies and forces (Figs. and) shows that the errors are again, well clustered around 0. The deviations in the error distributions stem from the fact that the spherical t-design grids are only symmetric about the upper and lower hemispheres and can produce slight differences for different components of the force or the energy depending on the orientation of the longrange cell relative to the atom under consideration.