<div dir="ltr">Dear CP2K folk, I have two questions about employing the &HF flag for a relatively large system. My system consists of a single molecule made up by 70 atoms. I am using the large basis of TZV2PX-MOLOPT-GTH-qx and the PBE0 functional with vdW correction. This is how I wrote the functional flag ###################################################### &XC &XC_FUNCTIONAL &PBE SCALE_X 0.75 SCALE_C 1.0 &END &END XC_FUNCTIONAL &XC_GRID XC_DERIV SPLINE2 &END &VDW_POTENTIAL POTENTIAL_TYPE PAIR_POTENTIAL &PAIR_POTENTIAL TYPE DFTD3 PARAMETER_FILE_NAME ./dftd3.dat REFERENCE_FUNCTIONAL PBE0 &END PAIR_POTENTIAL &END VDW_POTENTIAL &HF FRACTION 0.25 &MEMORY MAX_MEMORY 512 EPS_STORAGE_SCALING 1.0E-1 &END MEMORY &SCREENING EPS_SCHWARZ 1.0E-8 &END SCREENING &END HF &END XC ###################################################### The questions are: ) 1- I tested the functional on a small system of 3 atoms and that was done within hours. However, for the large system of 70 atoms the calculations took ages (and were finally interrupted due to resource limits). The questions is: Is this a normal calculation period for HF? Are there CP2K options that I can use to speed up the calculations? 2- When I checked what was printed out in the log file I found the following message: *** 22:23:54 WARNING in hfx_types:hfx_create_neighbor_cells :: Periodic *** *** Hartree Fock calculation requested without use of a truncated or *** *** shortrange potential. This may lead to unphysical total energies. Use *** *** a truncated potential to avoid possible problems. hfx_types.F line *** *** 1411 *** Since this is a single molecule (in a very large box), can I safely ignore the warning? Thanks, ER </div>