<div dir="ltr">I'm attempting to run MD using QS on a 64 molecule water box. So far I have been unable to achieve consistent performance across the MD trajectory. After a while the time per MD step dramatically increases, but the number of SCF iterations per step stays basically constant, as you can see in the included image.<a imageanchor="1" href="about:invalid#zClosurez" style="margin-left: 1em; margin-right: 1em;"><img src="cid:55068c28-700b-4db0-b7e7-3e2d01c50dcb" alt="md_timing.png" width="320" height="240" style="" border="0"></a>To further illustrate this, the following is from one of the first steps in the trajectory ----------------------------------- OT --------------------------------------- Minimizer : DIIS : direct inversion in the iterative subspace using 7 DIIS vectors safer DIIS on Preconditioner : FULL_ALL : diagonalization, state selective Precond_solver : DEFAULT stepsize : 0.15000000 energy_gap : 0.08000000 eps_taylor : 0.10000E-15 max_taylor : 4 ----------------------------------- OT --------------------------------------- Step Update method Time Convergence Total energy Change ------------------------------------------------------------------------------ 1 OT DIIS 0.15E+00 2.3 0.00030148 -1107.9047914512 -1.11E+03 2 OT DIIS 0.15E+00 1.6 0.00012826 -1107.9089080136 -4.12E-03 3 OT DIIS 0.15E+00 1.6 0.00007994 -1107.9095257164 -6.18E-04 4 OT DIIS 0.15E+00 1.6 0.00000744 -1107.9096948950 -1.69E-04 5 OT DIIS 0.15E+00 2.0 0.00000377 -1107.9096964458 -1.55E-06 6 OT DIIS 0.15E+00 1.6 0.00000067 -1107.9096967653 -3.19E-07 *** SCF run converged in 6 steps *** Electronic density on regular grids: -511.9999993695 0.0000006305 Core density on regular grids: 511.9999999846 -0.0000000154 Total charge density on r-space grids: 0.0000006151 <style type="text/css"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'PT Mono'; color: #000000} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'PT Mono'; color: #000000; min-height: 15.0px} span.s1 {font-variant-ligatures: no-common-ligatures} </style> Total charge density g-space grids: 0.0000006151 While after ~2500 steps, the same section now looks like ----------------------------------- OT --------------------------------------- Minimizer : DIIS : direct inversion in the iterative subspace using 7 DIIS vectors safer DIIS on Preconditioner : FULL_ALL : diagonalization, state selective Precond_solver : DEFAULT stepsize : 0.15000000 energy_gap : 0.08000000 eps_taylor : 0.10000E-15 max_taylor : 4 ----------------------------------- OT --------------------------------------- Step Update method Time Convergence Total energy Change ------------------------------------------------------------------------------ 1 OT DIIS 0.15E+00 6.3 0.00003184 -1108.0316770158 -1.11E+03 2 OT DIIS 0.15E+00 17.0 0.00001599 -1108.0317180830 -4.11E-05 3 OT DIIS 0.15E+00 18.4 0.00000956 -1108.0317247395 -6.66E-06 4 OT DIIS 0.15E+00 21.9 0.00000119 -1108.0317273970 -2.66E-06 5 OT DIIS 0.15E+00 6.8 0.00000063 -1108.0317274283 -3.14E-08 *** SCF run converged in 5 steps *** Electronic density on regular grids: -511.9999994472 0.0000005528 Core density on regular grids: 511.9999999845 -0.0000000155 Total charge density on r-space grids: 0.0000005373 <style type="text/css"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'PT Mono'; color: #000000} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 14.0px 'PT Mono'; color: #000000; min-height: 15.0px} span.s1 {font-variant-ligatures: no-common-ligatures} </style> Total charge density g-space grids: 0.0000005373 This has happened with different functionals, pseudopotentials, and SCF parameters (PS vs ASPC extrapolation, different orders of extrapolation, OT DIIS vs DIIS/Diag., different preconditioners). I recompiled the whole code with the toolchain install script generating all dependencies and got the same result. There is no indication from the dynamics of the system itself as to what the problem might be as the potential and kinetic energies are well behaved, and the constant of motion for the dynamics is reasonably conserved. I've watched the resulting trajectory itself, and there is nothing unusually happening (no bonding breaking, etc.) The input file I used for run in the plot above is attached. The starting geometry for the water molecules was taken from the 64 molecule benchmark in the tests/QS directory. If anyone has any suggestions on possible causes or where I can look for more information, I would be very appreciative.</div>