The effect of rcoulomb on the simulation

User discussions
1

Hi all,

I wanna know what is the effect of changing rcoulumb on the energy of the system and the cost of the simulation. If we use 1.5 compared to 1.0 for example, how much it will be affected?

Also, how should we define this number as I saw different numbers for the rcoulomb?

Thanks in advance,
Reza

2

With the simplest algorithm the cost would go up with rcoulomb^3, in practice in GROMACS it’s a bit less. But one would nearly always use PME for electrostatics and then one can use a coarser grid when increasing rcoulomb, so the cost goes up far less. Actually, with PME mdrun automatically increases rcoulomb, when useful, and chooses the optimal rcoulomb.

In your mdp file you would nearly always choose rcoulomb equal to rvdw and rvdw should set to what the should be used with the force field you use.