[gmx-users] Use NVT to mimic NVE
Michael Shirts
mrshirts at gmail.com
Mon Oct 13 17:02:53 CEST 2014
> I guess, if I pick a coupling constant that is just small enough to keep the
energy conserved, I would get a NVT simulation that is as close as a NVE
simulation as possible.
> Is this correct?
Yes, but then at that point the thermostat isn't actually thermostatting.
The Bussi comment is merely to show that his thermostat correctly reduces
to Newton's law in the limit, not that it would be useful to run it in that
limit.
On Mon, Oct 13, 2014 at 10:28 AM, Johnny Lu <johnny.lu128 at gmail.com> wrote:
> On page 014101-3, the Bussi paper (http://dx.doi.org/10.1063/1.2408420)
> mentioned: "On the other hand, for coupling constant approaching
> infinity,the Hamiltonian dynamics is recovered."
> Does that means that for a large enough coupling constant, the velocities
> are nearly not rescaled, and the dynamics (like rate of motion) would be
> same as that of NVE?
>
> A larger coupling constant, means a smaller diffusion coefficient in the
> axillary dynamics by equation 6.
>
> While the effects of the velocity rescaling at each step will accumulate, a
> larger coupling constant means the thermostat perturb less of the dynamics,
> and the resulting dynamics is closer to a NVE simulation.
> There is no worry that the thermostat would suddenly rescale the dynamics
> every x step, because in the procedure of the thermostat, the velocities
> are rescaled every step, regardless of the coupling constant.
>
> I guess, if I pick a coupling constant that is just small enough to keep
> the energy conserved, I would get a NVT simulation that is as close as a
> NVE simulation as possible.
>
> Is this correct?
> --
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