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[lammps-users] Question about using r-respa integrator
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[lammps-users] Question about using r-respa integrator

From: Pengyu Huang <>
Date: Thu, 12 Apr 2018 03:04:00 +1000

Dear all,

I would like to model flexible water, co2 and solid surfaces in my system with LAMMPS, which requires a very small time step (for flexible water), i.e. dt = 0.25 fs. I think r-respa may be one way to speed up the simulation. According to the LAMMPS document, it suggests using the following setup, so that the innermost time step is 0.5 fs:

timestep  4.0
run_style respa 4 2 2 2 inner 2 4.5 6.0 middle 3 8.0 10.0 outer 4  
I will try this set up in my simulations with timestep = 2 fs so that the innermost timestep is 0.25 fs (for bonds and angles) . My question is: apart from checking the energy conservation, is there any "pitfalls" about using the r-respa method in molecular dynamics simulations that I should pay attention to? It will be great if anyone who has had experiences with the r-respa method can provide any comments, suggestions or hints. All comments are welcome.

Thank you for your time.