<div dir="ltr">Hello Everyone, I have been running geometry optimisations of some quite large systems (~2000 electrons after pseudopotentials are used) with a hybrid HF/DFT functional (HSE06) and have been trying to fiddle with the HFx memory allocation to maximise performance. Using a combination of ADMM and the psmp executable on Archer with a lot of the available memory allocated to HFx, I have managed to bring the time per SCF step down quite considerably. However, the optimisation then will not run beyond a few steps before the program runs out of memory. Leaving even 2GB per MPI process for the rest of the program leads to it eventually running out of memory, and I have found that I cannot allocate more than half of the available memory if the geometry optimisation is to work for any reasonable length of time when using a CG optimiser. The CP2K manual implies that the different geometry optimisers (BFGS, LBFGS, CG etc) are best suited to different sizes of systems, but does this mean that some are more robust than others for larger systems, or does it mean that some are more efficient (and potentially less memory intensive) than others? Also, is there a good way of estimating how much memory the geometry optimiser will likely use, or any factors that typically affect memory consumption besides the system size alone? Best Regards -Peter </div>