where n 1 , n 2 , n 3 , n 4 and n 5 are the numbers of atoms, 2-body interactions, 3body interactions, 4-body interactions and periodic boxes within the long range cutoff, respectively. The coefficients c 1 through c 4 are indicators of the relative computational cost of their corresponding ReaxFF kernels. They can be determined empirically to accurately represent the computational costs in a given training set for a particular architecture. The cost of each cluster is determined by the computationally most expensive geometry within the cluster. This is determined by the max value between the current cluster center y and geometry x.