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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal>Dear QE users,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I am currently trying to run calculations on a 324-atom crystal system using DFT+U+V (I’m running a recompiled version of QE 7.2 with an increased natx parameter). More specifically, I am trying to use only the V parameter on the combination of two specific atomic orbitals which are supposed to form a polaronic dimer (the Hubbard potential is helping to localize the polaronic charge on the dimer after tuning). This worked well on smaller systems.<o:p></o:p></p><p class=MsoNormal>The issue that I’m facing with the large system is that the calculation is taking very long to initiate (~20 000 seconds), while the iterations themselves are relatively fast (~3000 seconds).This seems strange that the preliminary calculations take so much longer than the actual iterations. On smaller systems (96 atoms), I was not observing that trend, the bottleneck was the iterations as expected and there was barely any initialization time.<o:p></o:p></p><p class=MsoNormal>The most concerning aspect is that this bottleneck does not seem to be effectively distributed in parallel, because no matter how many nodes I use, the pre-iteration calculations always seem to take about 20 000 seconds (meanwhile, the iteration time does decrease when using more nodes)<o:p></o:p></p><p class=MsoNormal>The routine taking up all that time is the Hubbard routine “alloc_neigh”. I thought it might have been due to some memory issues, but looking at the memory usage of the nodes during the job, it seems to have only used about 30% of memory according to slurm “seff” utility. I have also experimented with different IO settings to try to reduce memory usage without success.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Is there a way to speed up that part of the calculation, or at least to distribute it over several nodes? Am I doing something wrong in my input? <o:p></o:p></p><p class=MsoNormal>Additionally, it seems that the program is calculating Hubbard projectors for every single atom of the species, even though I am only applying a V parameter on two hand-picked atoms, which seems very wasteful indeed. Is there a way to force the program to drop the Hubbard calculations on the atoms of the same species which do not receive a V value?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have attached the input and output file of an example job (charge has been set to 0 in that particular one, but same problem happens when adding the polaronic charge)<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Thanks in advance!<o:p></o:p></p><p class=MsoNormal>Julien<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>