brownian dynamics, damp and timestep

Hi All,

I am simulating some particles using brownian dyanmics with water as a solvent.

Let say, the particle mass (m) is 30 g/mole and radius (a) 0.5 nm. The water viscosity (eta) is 1.010^(-3) kg/(m.s). Avagadro number N = 6.02210^(23)

The damp parameter in fix langevin is equal to mass/(6pieta*a).

With the above parameters, damp = 5.3 fs. The temperature of the system is relaxed in a time span of damp (time units).

Which means the time step should be much smaller than the damp, 5.3 fs in this case.

This don’t seem to be right for Brownian dynamics.

I must be be missing something here, …