Dear CP2K users,<div> </div><div>I have been through different threads on this forum to understand how to optimize a cluster of 600 hundred atoms (see 0_tip3p_geom.xyz) with TIP3P model.</div><div> </div><div>1)I firstly tried this input taken from the FIST repository on GitHub <a href="https://github.com/cp2k/cp2k/blob/master/tests/Fist/regtest-4/H2O-1.inp">here</a></div><div>(see first_tip3p.inp) but I was always getting this error after the Optimization starts:</div><div>"WARNING| Particles: 600 598 at distance [au]: 1.82837959 less than: 2.00430963; increase EMAX_SPLINE.</div><div>GEOMETRY wrong or EMAX_SPLINE too small!"</div><div> </div><div> </div><div> </div><div> </div><div>2)The I moved to the other input reported in the same repository at this <a href="https://github.com/cp2k/cp2k/blob/master/tests/Fist/regtest-4/H2O-32_SPME_fp.inp.">link</a>, where more water molecules were included in the initial geometry. In this case (see second_tip3p.inp), the optimization starts but at a certain point it crashes again with a similar error: </div><div> </div><div>"WARNING| Particles: 600 598 at distance [au]: 0.89796367 less than: 0.95400000; increase EMAX_SPLINE."</div><div>GEOMETRY wrong or EMAX_SPLINE too small! At this point I am a little confused on how to proceed. I remembered that tip3p is a rigid FF and I started to look for constraining options for intramolecular distances and angles. I found in the same input of the above the section &CONSTRAINT &G3X3. 3) Thus, I defined the new input using this constrain that could probably explains the reason why CP2K was crushing before in this way (see third_tip3p.inp). However, also this test was unsuccessful with the following error: " | Error in constraints setup! | A constraint has been defined for a molecule type | but the atoms specified in the constraint and the atoms defined for | the molecule DO NOT match! | This could be very probable due to a wrong connectivity, or an error | in the constraint specification in the input file. | Please check it carefully!" Moreover, I also found in another thread <a href="https://groups.google.com/g/cp2k/c/ld5pmmYUnBk/m/iZte7XZGBwAJ">here</a>, that the specified constrained keyword works only for MD runs and not for GEO_OPT or CELL_OPT. At the moment I don't have any clue in how to proceed to obtain a optimized geometry with tip3p model. For this reason I would like to ask if anybody have ever optimized with tip3p model, or can help me for setting the proper input. Hope to hear from you. Kindly, Vittorio </div><div> </div> -- You received this message because you are subscribed to the Google Groups "cp2k" group. To unsubscribe from this group and stop receiving emails from it, send an email to <a href="mailto:cp2k+unsubscribe@googlegroups.com">cp2k+unsubscribe@googlegroups.com</a>. To view this discussion on the web visit <a href="https://groups.google.com/d/msgid/cp2k/e32370de-519b-4fd3-9176-438ddf027704n%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/e32370de-519b-4fd3-9176-438ddf027704n%40googlegroups.com</a>.