Re: ABF thermostats and energy introduced into the system

From: Ajasja Ljubetič (
Date: Tue Feb 26 2013 - 02:52:54 CST

> Just to be sure, you weren't using multiple time-stepping, right? Because
> MTS doesn't conserve energy either.

No, I'm not using MTS (and I also had a very conservative stepsize of .1

> Langevin with a very low damping constant should be okay (try 0.1 to see
> if it works).

Ok, I'll try (1/ps was the lowest I tried).

Thanks and best regards,

On Feb 25, 2013, at 8:07 AM, Ajasja Ljubetič wrote:
> Dear all,
> This next questions is similar to asking "I poured kerosene into my car --
> why did it explode?". But bear with me for the next paragraph, perhaps it
> is not so bad.
> I performed 400 ns of ABF simulations on the phi and psi angles of the
> alanine dipeptide in vacuum.
> Then I made a short run without using the thermostat. This was done on
> purpose and I did of course notice the warning printed by the colvars
> module. The net result of this was that my system heated up considerably.
> I realize that meta-dynamics always puts energy into the system, but I had
> the feeling that since ABF is a time dependant potential it could input
> energy in some bins and output energy in other, so that the net work done
> on the system would be small. So my questions are:
> - *Does ABF always pump energy into a system and what factors
> determine if energy goes in or out? *
> - *What thermostat is the most suitable for ABF? *(Langevin, tCouple,
> Lowe-Andersen, ...)
> Probably the best thermostat is the one that does not hinder diffusion
> too much, so the answer would be Lowe-Andersen, but that does not work with
> CUDA, so the next best is Langevin?
> Thank you for your help & best regards,
> Ajasja Ljubetic

This archive was generated by hypermail 2.1.6 : Wed Dec 31 2014 - 23:20:57 CST