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:
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.