<div>Hi,</div><div> </div><div>Taking the H2O-32_SPME.inp file and reducing the timestep to 2 fs I get no drift with NVT. </div><div> </div><div>In NVE there is still a little drift, but decreasing the SHAKE tolerance to 1.0E-07 this seems to be removed (see attached, changed the SHAKE tolerance at ~2.1 ns.</div><div> </div><div>In all cases the drift seems to be smaller than being reported, I think. Which version did you use? Mine is serial compiled under cygwin with internal FFTSG.</div><div> </div><div> "CP2K| version string: CP2K version 2.2.356 (Development Version) CP2K| is freely available from http://cp2k.berlios.de/ CP2K| Program compiled at Tue Sep 27 14:10:08 GMTDT 2011 CP2K| Program compiled on palliata CP2K| Program compiled for Cygwin-i686-gfortran" </div><div> </div><div>Matt</div> On Monday, September 24, 2012 9:36:07 AM UTC+1, jgh wrote:<blockquote class="gmail_quote" style="margin: 0;margin-left: 0.8ex;border-left: 1px #ccc solid;padding-left: 1ex;">Hi my guess is that you can get better results by tuning the Ewald parameters. I see the following sources of errors that can lead to drifts. 1) the cutoff for the LJ potential (there is no smoothing at the cutoff used) 2) An inadequate combination of length cutoff (real space), alpha and grid cutoff 3) timestep In CP2K the two cutoff in 1) and 2) are the same. A rule of thumb says alpha*rc should be at least 7 (0.5*11.4=5.7 in your case). To get better conservation of energy I would: - shorten the timestep (2fs probably) - increase the LJ cutoff (14) - increase alpha (1.) and the grid cutoff (more points) Warning: the grid cutoff is given as number of points, if you go to bigger systems you have to scale the number of points with the box size. I don't do long time simulations with classical force fields, so the values above are only guesses. regards Juerg -------------------------------------------------------------- Juerg Hutter Phone : ++41 44 635 4491 Physical Chemistry Institute FAX : ++41 44 635 6838 University of Zurich E-mail: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">hut...@pci.uzh.ch</a> Winterthurerstrasse 190 CH-8057 Zurich, Switzerland --------------------------------------------------------------- -----<a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">cp...@googlegroups.com</a> wrote: ----- To: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">cp...@googlegroups.com</a> From: paolo nicolini Sent by: <a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">cp...@googlegroups.com</a> Date: 09/21/2012 05:45PM Subject: Re: [CP2K:4045] Re: Energy conservation NVT/NVE simulation Hi I tried to use the H2O-32_SPME.inp in the tests/Fist directory by changing only the length of the simulation (1 ns) and I got also a significant energy drift (see attachment). Then I tried to reduce the integration time step to 1.0 fs. The drift become lower but it do not vanish. I did also 1ns of NVE dynamics (starting from the last restart of the previous simulations) and here the drift become even more clear. The inputs that I used are below. Best regards Paolo NVT input: &FORCE_EVAL METHOD FIST &MM &FORCEFIELD &BEND ATOMS H O H K 0. THETA0 1.8 &END BEND &BOND ATOMS O H K 0. R0 1.8 &END BOND &CHARGE ATOM O CHARGE -0.8476 &END CHARGE &CHARGE ATOM H CHARGE 0.4238 &END CHARGE &NONBONDED &LENNARD-JONES atoms O O EPSILON 78.198 SIGMA 3.166 RCUT 11.4 &END LENNARD-JONES &LENNARD-JONES atoms O H EPSILON 0.0 SIGMA 3.6705 RCUT 11.4 &END LENNARD-JONES &LENNARD-JONES atoms H H EPSILON 0.0 SIGMA 3.30523 RCUT 11.4 &END LENNARD-JONES &END NONBONDED &END FORCEFIELD &POISSON &EWALD EWALD_TYPE spme ALPHA .5 GMAX 21 O_SPLINE 6 &END EWALD &END POISSON &END MM &SUBSYS &CELL ABC 9.865 9.865 9.865 &END CELL &COORD O -4.583 5.333 1.560 H2O H -3.777 5.331 0.943 H2O H -5.081 4.589 1.176 H2O ... &END COORD &END SUBSYS &END FORCE_EVAL &GLOBAL PROJECT H2O RUN_TYPE MD &END GLOBAL &MOTION &CONSTRAINT &G3X3 DISTANCES 1.8897268 1.8897268 3.0859239 MOLECULE 1 ATOMS 1 2 3 &END G3X3 &END CONSTRAINT &MD ENSEMBLE NVT STEPS 1000000 TIMESTEP 1.0 TEMPERATURE 300.0 &THERMOSTAT REGION MOLECULE &NOSE LENGTH 3 YOSHIDA 3 TIMECON 1000 MTS 2 &END NOSE &END &END MD &END MOTION NVE input: &FORCE_EVAL METHOD FIST &MM &FORCEFIELD &BEND ATOMS H O H K 0. THETA0 1.8 &END BEND &BOND ATOMS O H K 0. R0 1.8 &END BOND &CHARGE ATOM O CHARGE -0.8476 &END CHARGE &CHARGE ATOM H CHARGE 0.4238 &END CHARGE &NONBONDED &LENNARD-JONES atoms O O EPSILON 78.198 SIGMA 3.166 RCUT 11.4 &END LENNARD-JONES &LENNARD-JONES atoms O H EPSILON 0.0 SIGMA 3.6705 RCUT 11.4 &END LENNARD-JONES &LENNARD-JONES atoms H H EPSILON 0.0 SIGMA 3.30523 RCUT 11.4 &END LENNARD-JONES &END NONBONDED &END FORCEFIELD &POISSON &EWALD EWALD_TYPE spme ALPHA .5 GMAX 21 O_SPLINE 6 &END EWALD &END POISSON &END MM &END FORCE_EVAL &GLOBAL PROJECT H2O RUN_TYPE MD &END GLOBAL &MOTION &CONSTRAINT &G3X3 DISTANCES 1.8897268 1.8897268 3.0859239 MOLECULE 1 ATOMS 1 2 3 &END G3X3 &END CONSTRAINT &MD ENSEMBLE NVE STEPS 1000000 TIMESTEP 1.0 TEMPERATURE 300.0 &END MD &END MOTION &EXT_RESTART RESTART_FILE_NAME H2O-1_1000000.restart &END EXT_RESTART On Monday, September 17, 2012 1:09:54 PM UTC+2, jgh wrote:Hi I did some tests with the inputs from ../tests/Fist and get much better energy conservation that you show. Probably your input use a not optimal setting for the cutoffs and Ewald parameters (I was using SPME). regards Juerg -------------------------------------------------------------- Juerg Hutter Phone : ++41 44 635 4491 Physical Chemistry Institute FAX : ++41 44 635 6838 University of Zurich E-mail: <a>hut...@pci.uzh.ch</a> Winterthurerstrasse 190 CH-8057 Zurich, Switzerland --------------------------------------------------------------- -----<a>cp...@googlegroups.com</a> wrote: ----- To: <a>cp...@googlegroups.com</a> From: marco masia Sent by: <a>cp...@googlegroups.com</a> Date: 09/12/2012 03:39PM Subject: [CP2K:4029] Re: Energy conservation NVT/NVE simulation Dear all, recently I have noticed the same problem with FIST simulations. I took the H2O-32_ewald.inp input, equilibrated it for 1 ns and run a 1ns NVE simulation from the thermalized configuration. I have tried to refine many simulation parameters (e.g. time step, RCUT, Ewald pars) and also (thinking that there was a bad implementation of constraints) I run the simulations for a flexible model. I always get a non-negligible drift (see attachment); the graph shows block averaged energies of 1 ns simulations performed with cp2k and obeli.x (a program of mine). The values are shifted for a better comparison. I have been looking into this, thinking that the problem was in the input file...but since other people are experiencing it with QS, I wonder if there is some bug in the velocity verlet routines. The results are platform independent (I tried both on mac and linux). best marco On Wednesday, September 5, 2012 3:32:26 AM UTC-4, <a>albe...@virgilio.it</a> wrote: Dear all, I'm carrying out some tests to reproduce the VDOS of water and I used as starting points the input files 'H2O-32.inp' and 'H2O-64.inp' in tests/QS/benchmark directory. In both cases I ran a NVT simulation at 300K for 15 ps followed by an NVE simulation on the equilibrated system. I'm puzzled about the results in the energies: in both NVT and NVE the plot of "Cons Qty" show a constant and linear drift while temperature, kinetic and potential energy are equilibrated and stable. Since "Cons Qty" should be conserved and this is not the case I think that there are some problems in the setup of the simulation. I did not modify the parameters of the benchmark inputs but I just added the thermostat section in NVT and I modified only the printing option. Thank you very much for your help and suggestions, Alberto -- You received this message because you are subscribed to the Google Groups "cp2k" group. To view this discussion on the web visit <a href="https://groups.google.com/d/msg/cp2k/-/sAiVZ2dob1sJ" target="_blank">https://groups.google.com/d/msg/cp2k/-/sAiVZ2dob1sJ</a>. To post to this group, send email to <a>cp...@googlegroups.com</a>. To unsubscribe from this group, send email to <a>cp2k+...@googlegroups.com</a>. For more options, visit this group at <a href="http://groups.google.com/group/cp2k?hl=en" target="_blank">http://groups.google.com/group/cp2k?hl=en</a>. [attachment "energy-conservation.pdf" removed by Jürg Hutter/at/UZH] -- You received this message because you are subscribed to the Google Groups "cp2k" group. To view this discussion on the web visit <a href="https://groups.google.com/d/msg/cp2k/-/nmvFu5yyMKQJ" target="_blank">https://groups.google.com/d/msg/cp2k/-/nmvFu5yyMKQJ</a>. To post to this group, send email to <a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">cp...@googlegroups.com</a>. To unsubscribe from this group, send email to <a href="javascript:" target="_blank" gdf-obfuscated-mailto="vnUFX5-wI2wJ">cp2k+...@googlegroups.com</a>. For more options, visit this group at <a href="http://groups.google.com/group/cp2k?hl=en" target="_blank">http://groups.google.com/group/cp2k?hl=en</a>. [attachment "all.pdf" removed by Jürg Hutter/at/UZH]</blockquote>