<div dir="ltr">Hello Juerg,<div>Thank you for your reply. I added REFERENCE_C9_TERM .TRUE. to the vdw section as you suggested and found that my MD simulation became twice (!) as fast. That is, time per MD step went from ~60 sec to ~30 sec for box of water with 64 molecules and K,Cl ions. I made a quick comparison of Energy_Force results with and without this flag and indeed forces and energies do not change significantly. This is great news. Why is this not a default? What's the catch? Also, would you say this is now a correct way to declare a PBE-D3 setup?</div><div><br></div><div><br></div><div><div>&VDW_POTENTIAL</div><div> POTENTIAL_TYPE PAIR_POTENTIAL</div><div> &PAIR_POTENTIAL</div><div> R_CUTOFF 1.5000000000000005E+01</div><div> TYPE DFTD3</div><div> PARAMETER_FILE_NAME dftd3.dat</div><div> REFERENCE_FUNCTIONAL PBE</div><div> CALCULATE_C9_TERM T</div><div> REFERENCE_C9_TERM T</div><div> &END PAIR_POTENTIAL</div><div> &END VDW_POTENTIAL</div></div><div><br></div><div>Finally, I mentioned earlier that 30 scf steps were needed to converge the same box of water with ions. I was then using EPS_SCF = 1E-06. Reducing this to EPS_SCF = 1E-05 brought the number down to 10-20 scf necessary. Does that still sound high? Is the definition of EPS_SCF documented somewhere, as it is apparently not just Energy convergence. </div><div><br></div><div>Cheers,</div><div>Simiam Ghan</div><div><br></div><div><br></div><div><br><div><br>On Friday, July 1, 2016 at 3:10:52 PM UTC+3, jgh wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">Hi
<br>
<br>no this shouldn't be, but without more information I will have to guess.
<br>You could also have a look at the timings at the end of the output to
<br>see if some routines got slower or if all parts of the run were affected.
<br>
<br>Two things to consider:
<br>
<br>1) Use REFERENCE_C9_TERM TRUE in order to reduce the time for vdW in MD.
<br>2) 30 SCF iterations in MD for such a simple system is pointing to a problem
<br> with your setup.
<br>
<br>regards
<br>
<br>Juerg
<br>------------------------------<wbr>------------------------------<wbr>--
<br>Juerg Hutter <wbr> Phone : ++41 44 635 4491
<br>Institut für Chemie C FAX : ++41 44 635 6838
<br>Universität Zürich E-<wbr>mail: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="BrXPU-3iBQAJ" rel="nofollow" onmousedown="this.href='javascript:';return true;" onclick="this.href='javascript:';return true;">hut...@chem.uzh.ch</a>
<br>Winterthurerstrasse 190
<br>CH-8057 Zürich, Switzerland
<br>------------------------------<wbr>------------------------------<wbr>---
<br>
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<br>From: Simiam Ghan
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<br>Date: 07/01/2016 01:38PM
<br>Subject: [CP2K:7883] SCF, MD run-time verses atomic species.
<br>
<br>Dear all,I am running NVT MD with Quickstep on a box of water with 64 molecules. If I replace a water molecule with a KCl ion pair, i observe that the MD and SCF step times more than double on my setup. (MD from ~20 sec to ~46 sec). SCF iterations are converging (except the very first MD step) in around 30 steps in both cases but each SCF now takes over twice as long as before. Is there an explanation of why such a 'small' change in system could double the run time? Is KCl really so heavy to calculate compared to H2O? The number of electrons in the system increases by 8, from 512 to 520. Below my KCl input file.
<br>Greetings,Simiam
<br>
<br>
<br>&GLOBAL
<br> PROJECT H2O_KCl RUN_TYPE MD PRINT_LEVEL MEDIUM
<br>&END GLOBAL
<br>&FORCE_EVAL
<br> METHOD Quickstep ! GPW method.
<br> &SUBSYS ! A subsystem: coordinates, topology, molecules and cell.
<br> &CELL ! Supercell setup. ABC [angstrom] 12.414 12.414 12.414 ! Using 64 H2O molecules, we thus get a density of 1g/cm^3. PERIODIC XYZ ! Use PBC in all dimensions. &END CELL
<br> &COORD UNIT angstromH -0.567712 -0.469646 -0.645913H 0.626116 -0.687796 0.308193O 0 0 0(...)K 2.1035 2.1035 4.2735Cl 4.1035 4.1035 2.6035 ###H 3.73881 3.10388 5.46104
<br>H 3.65742 2.89924 6.989O 3.1035 3.1035 6.207(...) &END COORD
<br> &KIND O BASIS_SET DZVP-MOLOPT-GTH-q6 POTENTIAL GTH-PBE-q6 &END KIND &KIND H BASIS_SET DZVP-MOLOPT-GTH-q1 POTENTIAL GTH-PBE-q1 &END KIND &KIND K BASIS_SET DZVP-MOLOPT-SR-GTH-q9 POTENTIAL GTH-PBE-q9 &END KIND &KIND Cl BASIS_SET DZVP-MOLOPT-GTH-q7 POTENTIAL GTH-PBE-q7 &END KIND
<br>
<br>
<br>
<br>
<br> &END SUBSYS
<br> &DFT
<br> BASIS_SET_FILE_NAME BASIS_MOLOPT POTENTIAL_FILE_NAME GTH_POTENTIALS ! SPIN_POLARIZED ! Do spin-polarized calculation
<br> &POISSON PERIODIC XYZ &END POISSON
<br> &QS METHOD GPW EPS_DEFAULT 1.0E-10 ! Set various epsilons for QS to values that will lead ! to energy correct up to 1e-10. &END QS
<br> &MGRID CUTOFF 400 ! This is Ecut of eq. 39 in VandeVondele (2005), i.e., plane-wave cutoff ! that determines size of finest grid (see caption of Fig. 1). Cutoffs for ! the subsequent, coarser grid levels are given by eq. 39. NGRIDS 4 ! This is N of eq. 39 in VandeVondele (2005), i.e., number of grids used. REL_CUTOFF 40 ! This controls the grid level onto which Gaussians will be mapped. &END MGRID
<br> &XC
<br> &XC_FUNCTIONAL &PBE PARAMETRIZATION ORIG &END PBE &END XC_FUNCTIONAL
<br> &VDW_POTENTIAL
<br> POTENTIAL_TYPE PAIR_POTENTIAL
<br> &PAIR_POTENTIAL TYPE DFTD3 REFERENCE_FUNCTIONAL PBE CALCULATE_C9_TERM .TRUE. PARAMETER_FILE_NAME dftd3.dat R_CUTOFF 15.0 &END PAIR_POTENTIAL
<br> &END VDW_POTENTIAL
<br> &END XC
<br> &SCF
<br> SCF_GUESS RESTART ! Use data from previous run as initial guess for wavefunction. EPS_SCF 1.0E-6 ! Threshold for converged total energy. MAX_SCF 300 ! Maximum number of SCF iterations performed.
<br> &OT PRECONDITIONER NONE ! This should be stable with respect to the "Cholesky errors" &END OT
<br> &PRINT &RESTART ON
<br> BACKUP_COPIES 1
<br> &EACH MD 1 &END EACH
<br> ADD_LAST NUMERIC
<br> &END RESTART
<br> &END PRINT
<br> &END SCF
<br> &PRINT &E_DENSITY_CUBE
<br> STRIDE 1 1 1
<br> &EACH MD 99999999 &END EACH
<br> ADD_LAST NUMERIC &END E_DENSITY_CUBE
<br> &PDOS COMPONENTS .FALSE. NLUMO = -1 FILENAME dosfile LOG_PRINT_KEY TRUE
<br> &EACH MD 99999999 &END EACH
<br> ADD_LAST NUMERIC &END PDOS
<br> &END PRINT
<br> &END DFT
<br>&END FORCE_EVAL
<br>&MOTION
<br> &MD ENSEMBLE NVT STEPS 10000 TEMPERATURE 300.0 ! K TIMESTEP 0.5 ! fs &THERMOSTAT
<br> REGION GLOBAL TYPE NOSE
<br> &NOSE LENGTH 3 ! Length of Nose-Hoover chain TIMECON 20.0 ! Period of typical vibrational motion in system in fs &END NOSE &END THERMOSTAT &END MD
<br> &PRINT
<br> &RESTART
<br> &EACH MD 1 &END EACH
<br> ADD_LAST NUMERIC
<br> &END RESTART
<br> &TRAJECTORY ON ADD_LAST NUMERIC FILENAME trajectory &END TRAJECTORY
<br> &END PRINT
<br>&END MOTION
<br>
<br>
<br>
<br>
<br>
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