Re: [ESPResSo-users] Langevin vs. Berendsen thermostat

[Stefan Kesselheim]

Hi Koen,
I'm not sure what paper we mention but there is a very fundamental difference: 
Using Langevin thermostat means that our particles follow the Langevin equation 
of motion, which is basically Newton's plus a friction and a noise term on 
every particle. Thus the dynamics become intrinsically stochastic. You find 
more about the Langevin equation in most textbooks on non equilibrium stat mech.
With the Berendsen thermostat Newton's equation of motion are modified such 
that in regular intervals the velocities are rescaled so that the total kinetic 
energy = 3/2*n*k_B T. 

Langevin is purely local (for Berendsen you need to sum up the kinetic energies 
over all CPUs) and it is much more effective and stable in thermalising dilute 
systems. See e.g.
http://en.wikipedia.org/wiki/Flying_ice_cube

This is why we do Langevin :-).

Cheers
Stefan


On Apr 26, 2013, at 11:09 AM, Koen Nickmans <address@hidden> wrote:

> Dear all,
> 
> I'm sorry this is not so much Espresso related, but would somebody be so kind 
> as to point a master student in the right direction as to what the difference 
> is between the Langevin and Berendsen thermostats, if there is one? The 
> Espresso user guide lists a Berendsen paper as a reference to the Langevin 
> thermostat, hence my confusion.
> 
> Thanks
> Koen Nickmans
> 
> -- 
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