Hi,<div> </div><div>I was trying to implement TIP4P/2005f force field in CP2K. I have setup the relevant forcefield and geometry section in the following manner:</div><div> </div><div>&FORCE_EVAL METHOD FIST &MM &FORCEFIELD &SPLINE EMAX_SPLINE 1.0E+128 RCUT_NB 12.0 &END SPLINE &BEND ATOMS HW OW HW THETA0 [deg] 107.4 K [rad^2kjmol] 367.810 KIND G87 &END BEND &BEND ATOMS HW OW MW THETA0 [deg] 53.7 !K [rad^2kjmol] 418.400 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BEND ATOMS MW HW OW THETA0 [deg] 107.4 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BEND ATOMS MW HW HW THETA0 [deg] 107.4 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BEND ATOMS OW HW HW THETA0 [deg] 107.4 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BEND ATOMS OW MW HW THETA0 [deg] 107.4 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BEND ATOMS HW MW HW THETA0 [deg] 107.4 K [rad^2kjmol] 0.000 KIND G87 &END BEND &BOND ATOMS OW HW K [kjmol] 432.581 [nm^-1] 22.87 R0 [nm] 0.09419 KIND MORSE &END BOND &BOND ATOMS OW MW K [nm^-2kjmol] 753120.0 !K [nm^-2kjmol] 00.0 R0 [nm] 0.01750 KIND G87 &END BOND &BOND ATOMS HW HW K [nm^-2kjmol] 000000.0 R0 [nm] 0.01750 KIND G87 &END BOND &BOND ATOMS HW MW K [nm^-2kjmol] 000000.0 R0 [nm] 0.01750 KIND G87 &END BOND &NONBONDED &LENNARD-JONES ATOMS OW OW EPSILON [kjmol] 0.77490 SIGMA [nm] 3.1644E-1 &END LENNARD-JONES &LENNARD-JONES ATOMS OW MW EPSILON 0.0 SIGMA 0.1 &END LENNARD-JONES &LENNARD-JONES ATOMS OW HW EPSILON 0.0 SIGMA 0.1 &END LENNARD-JONES &LENNARD-JONES ATOMS HW HW EPSILON 0.0 SIGMA 0.1 &END LENNARD-JONES &LENNARD-JONES ATOMS HW MW EPSILON 0.0 SIGMA 0.1 &END LENNARD-JONES &LENNARD-JONES ATOMS MW MW EPSILON 0.0 SIGMA 0.1 &END LENNARD-JONES &END NONBONDED &CHARGE ATOM OW CHARGE 0.000000 &END CHARGE &CHARGE ATOM HW CHARGE 0.52 &END CHARGE &CHARGE ATOM MW CHARGE -1.04 &END CHARGE &END FORCEFIELD &POISSON &EWALD EWALD_TYPE SPME ALPHA .44 GMAX 11 O_SPLINE 4 &END EWALD &END POISSON &END MM &SUBSYS &CELL ABC 8 8 8 &END CELL &COORD OW 2.4532128864011757E+01 2.9058620209822454E+01 3.8939754250319247E+01 H2O 1 HW 2.5226244482849356E+01 2.9202964725171807E+01 3.8296636945801339E+01 H2O 1 HW 2.4993856984368403E+01 2.8952666650621637E+01 3.9771507029174259E+01 H2O 1 MW 2.4684627509816810E+01 2.9063685400405998E+01 3.8964642263648159E+01 H2O 1 &END COORD &COLVAR &ANGLE ATOMS 1 2 3 &END ANGLE &END COLVAR </div><div> </div><div>Additionally I am using VIRTUAL_ATOMS section for the TIP4P virtual site, and I had fixed the H-O-H angle to cross check the implementation. When I ran the simulation I observed that the O-H distance seemed to vary between 0.6 to 1.7 angstroms which seems a bit too high for water NVE run at 300K. If the remove the H-O-H angle constraint, the water molecule completely dissociates. Does anyone have any suggestions or ideas on how to effectively setup this forcefield model in CP2K, or what should I correct in my input file?</div><div> </div><div>Best Regards</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/22d4e3fc-4ae6-4dd4-894d-feb82860057an%40googlegroups.com?utm_medium=email&utm_source=footer">https://groups.google.com/d/msgid/cp2k/22d4e3fc-4ae6-4dd4-894d-feb82860057an%40googlegroups.com</a>.