Re: [ESPResSo-users] Mass scale in simulations

[address@hidden]

Dear David,

In my opinion, if you don't activate the "MASS" feature, then all the particles have the same reduced mass of 1. And the resulting time scale is 

[time] = [length] \sqrt{  [mass] / [energy] } as the document said.

So the time scale is  independent of the number of particles.

Regards!

Ricky

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address@hidden

 

From: Geiseld

Date: 2019-05-22 18:10

To: espressomd-users

Subject: [ESPResSo-users] Mass scale in simulations

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.