With increasing system size, however, the SCF optimization will eventually start to become a computational bottleneck due to the O(N 3 )-scaling of the diagonalization of the Fock matrix and which is performed in every iteration of the SCF-driver to obtain molecular orbitals (MOs) and form an updated density matrix. We carry out this matrix diagonalization on a single GPU node with use of the MAGMA library 45 (version 2.8.0) for linear algebra on AMD GPUs using the HIP programming model. 46 In Table , we present wall clock timings for all parts of the calculations that are significant to the overall performance, and we do so for the small, medium, and large models of the G-quadruplex that will be presented below in detail. In this range of system sizes (up to some 12,000 basis functions), the results amply demonstrate that the contraction of ERIs with density matrices by a wide margin represents the most costly part of the calculation.