To elaborate on what Teo said, (he can correct me if I am wrong) In NVT, the total energy of the *real sytem + thermostat* should be conserved. (I don't remember if CP2K outputs this quantity, but most codes should). The total energy of just the real system (atoms,molecules,etc.) should have a mean value (after equilibration) with fluctuations proportional to 1/sqrt(N) (or something like that). If the total energy of the real system increases or decreases without bounds, then there is something wrong. Or maybe you are near some phase transition. <div class="gmail_quote">On Mon, Mar 10, 2008 at 4:37 PM, Teodoro Laino <<a href="mailto:teodor...@gmail.com">teodor...@gmail.com</a>> wrote: <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> Ciao Diederica, <div class="Ih2E3d"> > > These are added, as an attachment this time </div>Thanks.. will look into this problem ASAP. <div class="Ih2E3d"> > I'm modelling an isolated molecule, it should fit in the box. Using > NVE without temperature rescaling, with an analogue structure, an > energy drift was observed, that got worse after about 20 ps, though > no non-convergence was observed. The input file and an energy-plot > are added. </div>If you have a drift with NVE this means that energy and forces are not consistent.. or (what I assume) that the cutoff for the coulomb interactions is not large enough.. Please put all of the RC_COULOMB and RC_INTERACTION and RC_RANGE to 50.0. You've the problem that in your cell the standard range (24 bohr) does not fully cover the extension of your molecule (more than 26 bohr). Use a larger box (30.0 Angstrom) and set the above keywords to 50.0 bohr. You should not see any jump in the energy (or drift).. <div class="Ih2E3d"> > The potential and kinetic energy are conserved indeed, but the > conserved quantity is not </div>Sorry to disprove you, but it is not possible that in an NVT you have kinetic and potential conserved, since the thermostat is continuously exchanging energy with the system. I't s a matter of concept.. we may discuss about the magnitude of the thermostat energy.. but that's another story.. Cheers teo <div class="Ih2E3d"> > > > > For the next time, can you please put tables and input files as > attachment (maybe .tgz) so that the formatting of mail readers are > not changed and the input files not digested ? Thanks.. > > Ciao, > teo > > Thanks for helping! > > Greetz, > Diederica > > > > > > </div>> <mailcp2k.tgz> <div><div></div><div class="Wj3C7c"> </div></div></blockquote></div> -- Nichols A. Romero, Ph.D. DoD User Productivity Enhancement and Technology Transfer (PET) Group High Performance Technologies, Inc. Reston, VA 443-567-8328 (C) 410-278-2692 (O)