[ESPResSo-users] Mass scale in simulations

[Geiseld]

Dear all,

I have a question concerning the mass scale of the simulations in espresso.
The documentation states that

"By default, ESPResSo uses a reduced mass of 1,
so that the mass unit is simply the mass of all particles."
(http://espressomd.org/html/doc/introduction.html#on-units)

How is this statement to be interpreted? Does the time scale of my  
simulations change
when I add particles to the simulation, like

[time] = [length] \sqrt{ #particles* [mass] / [energy] }

or do I still only use the mass of one particle and assume that all  
particles have the same mass?

To test this I constructed a simple simulation of diffusing particles  
and calculated the
diffusion coefficient of a single particle (which should be  
independent of the number of
particles in the box (no interactions)).
Here, it seemed as if the time scale was independent of the number of  
particles. Is this correct?

I would be very thankful for advise,

best regards,
David.