TIP4P water model

LAMMPS LAMMPS General Discussion
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1

Dear LAMMPS Users,

I am currently trying to model a simple system using the TIP4P2005 water model, following the instructions provided in the LAMMPS documentation [8.4.4. TIP4P water model — LAMMPS documentation](https://Howto: TIP4P Water). I am using the second approach outlined in the guide, which employs the explicit 4-point TIP4P geometry.

I generated the water molecules using Packmol and created the data file with topotools, using the atom_style full as recommended in the guide. However, when I run the simulation, the system “blows up” after just a few timesteps.

I’ve attached my input script and data file for reference. I would greatly appreciate any insights or advice on what could be causing this issue.

Thank you in advance for your help!

Best regards,

Ehsan

data.water (4.9 KB)
input.in (942 Bytes)

2

From looking at your input, I would guess that the problem is the minimization. That would mess up your geometry. First of all, the command is placed before fix rigid and second you cannot do a minimization with rigid bodies.

Using fix shake and tip4p pair styles will be compatible with minimization (if your LAMMPS version is sufficiently recent).

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3

Also, you didn’t control your input script before posting it, e.g. the fix rigid/small is applied to a group that is not defined.

I suggest the following modifications:

  • remove the minimize command.
  • mass 1 1.0e-8    # e-100, really?
pair_style lj/cut/coul/cut 12.0
fix integrate_water all rigid/small molecule langevin 300.0 300.0 $(100*dt) 2345634

With the following modifications, you can also use a timestep up to 1 fs.

1 Like
4

Dear Axel and Otello,

Thank you very much for your reply. The problem was with minimization as you recommended. Sorry for the mistake in my input file it should be “all”.

5

Deal LAMMPS users,

I tried to run the same system but for a larger system (3000 water molecules) now I get this error upon running the simulation:

ERROR on proc 0: Rigid body atoms 631 632 missing on proc 0 at step 57 (src/RIGID/fix_rigid_small.cpp:3397)
Last command: run 40000

The updated input and data files are attached.

Any suggestion would be appreciated.
data.water (684.4 KB)
input.in (733 Bytes)

6

Hello,

Your initial energy is crazy high. Probably some overlap, it gets better after using the delete_atoms command, which suggests some issue with your data file.

Simon

1 Like