Having established that the ERI-part of the Fock matrix construction dominates the computational cost for system sizes of interest for running on GPU-accelerated clusters, we turn to the observed scaling behaviors of our software implementation. In Fig. , we present the scaling with respect to system size by keeping the resource constant (one node with four GPUs) while increasing the size of the spherical water droplet. This is a dense 3D system and our observations should thus not be contaminated by artificial sparsity and favorable screening that can be found in systems of more 1D or 2D character. The ratio between "heavy" and hydrogen atoms is here 1:2 which is quite representative albeit somewhat lower , here illustrated by a G-quadruplex including all nucleotides where the phosphate group has been neutralized by adding a hydrogen. Potassium ions and environment have been removed. In both cases, the def2-SVP basis set was adopted.