I am trying to use drude model on a box of water. Through LAMMPS tutorials I understood the commands for NVT and NPT runs, but for energy minimization and temperature ramping I couldn’t find anything. I prepared input files for the energy minimization and temperature ramping (inc), though it’s not throwing any error, but I wanted to confirm if it’s possible or not.
Another thing in temperature ramping step I had set initial temperature to be 5K and final 300K, and the temperature in output file is around 4.8K only. I couldn’t understand this.
I have attached the input files. Please help me understand this.
Thanks,
Megha
Your questions are very specific to the DRUDE package in LAMMPS. As so many features in LAMMPS, this is a contributed package and the expertise in using it correctly is not as common and for other parts of LAMMPS.
Since nobody has replied to your post so far, we have to assume that none of the people regularly looking to answer questions here know enough about apply Drude oscillator polarization. Thus my suggestion is to contact the authors of the DRUDE package. Their names and contact info should be listed either in the documentation or in a README file in the src/DRUDE folder or in the individual source files.
I have checked all the examples in \PACKAGES\drude, there is no energy minimization before the thermostat or barostat run.
and I tried to include energy minimization for all examples that thermostat with langevin, all of them can run without error (like in.butane.lang.lmp, in.ethanol.lang.lmp, in.toluene.lang.lmp), except for in.swm4-ndp.lang.lmp, I got error and info during minimization is shown below, the potential energy is extremely large:
Setting up cg style minimization …
Unit style : real
Current step : 0
Per MPI rank memory allocation (min/avg/max) = 27.75 | 27.75 | 27.75 Mbytes
Step Temp E_pair E_mol TotEng Press
0 0 3041.1655 623.46454 3664.63 84290.635
40 0 -8.2107776e+16 5519.9121 -8.2107776e+16 -1.7870642e+17
and it also happened in my case, if I don’t include swm4-ndp water in the system, the energy minimization goes well, but if swm4-ndp water is in my system, then the extremely large potential energy happens after minimization.
I was wondering if this is specific for swm4-ndp water, and if anyone can spot what could be the reason.
I already pointed out the “M” point situation to you. This can only work when the geometry (H, H, O, M) is held rigid. But there is no support for fix rigid during minimization. The only two ways to minimize such as system is to use simulated annealing or to add very stiff bonds from point M to all other water atoms during minimization, and then have an external program correct the geometry after the minimization.