I want to simulate the formation of surfactant/nanoparticle micelles in water box and its effect on shear viscosity of the liquid. The force field I use is Martini force field which is commonly used in Gromacs. Lammps provide five different methods to compute the viscosity, and this is why I chose it.
(1) For Martini FF in Gromacs, LJ interactions are shifted to zero in the range 0.9-1.2 nm, and electrostatic interactions in the range 0.0-1.2 nm. I noticed there is also a pairstyle in Lammps can describe this, i.e. lj/gromacs/coul/gromacs. But in this case, PPPM cannot be applied to compute the long-ranged electrostatic interactions. My question here is which pairstyle is good for Martini FF coupled with PPPM.
(2) Besides, I also try to use “lj/cut/coul/long” to set the cut-off, and use “pair-modify shift yes” to make both shit to zero at cutoff. But this shift from 0 to cutoff is a bit different from what Martini FF requires in Gromacs. If there is no better pairstyle in lammps to describe Martini FF, can I just use this instead and then I can also use PPPM?
(3) The third question may be not firmly related to the Lammps application. For martini FF, it is parameterized with short range shited exlectrostatic interaction, and it is not recommended to use PME in Gromacs to compute electrostatic interactions, especially for the standard water model. But why so many people using Lammps simulate the viscous flow of liquid try to use PPPM to calculated the long range electrostatic force? After all, electrostatic interactions in the Martini model are not considered to be very accurate.