[gmx-users] Use NVT to mimic NVE

[Johnny Lu]

I tried NVE on single precision gromacs 4.6.7 with and without GPU.
The energy either drift down or up, depending on the mdp file, and the
drift seems linear.

Linear fit says that if I run 100 ns simulation, at the end the energy is
doubled.

If I use double precision gromacs, the drift seems insignificant over 100
ns simulation by linear regression fitting on a 300 ps run.
But double precision gromacs can't use gpu and is much slower than single
precision gromacs.

On Sat, Oct 11, 2014 at 4:33 PM, Dr. Vitaly Chaban <vvchaban at gmail.com>
wrote:

> I also cannot get why not to just turn off the thermostat...
>
> If energy transfer phenomena are in focus, NVE is an ensemble of
> choice, no matter which relaxation constant is used for the T-coupling
> algorithm.
>
>
> Dr. Vitaly V. Chaban
>
> Виталий Витальевич ЧАБАН
>
>
> On Sat, Oct 11, 2014 at 6:32 PM, Antonio Baptista <baptista at itqb.unl.pt>
> wrote:
> > Then, run true NVE, for the reasons we already pointed.
> >
> > On Sat, 11 Oct 2014, Johnny Lu wrote:
> >
> >> For dynamics with correct rate and correct fluctuation.
> >>
> >> On Sat, Oct 11, 2014 at 8:09 AM, Dr. Vitaly Chaban <vvchaban at gmail.com>
> >> wrote:
> >>
> >>> what is it needed for?
> >>>
> >>>
> >>>
> >>> Dr. Vitaly V. Chaban
> >>>
> >>> Виталий Витальевич ЧАБАН
> >>>
> >>>
> >>> On Fri, Oct 10, 2014 at 7:41 PM, Johnny Lu <johnny.lu128 at gmail.com>
> >>> wrote:
> >>> > Hi.
> >>> >
> >>> > Is it a good idea to mimic NVE by a NVT simulation with a large
> >>> temperature
> >>> > coupling time constant, to reduce the effect of the thermostat ?
> >>> >
> >>> > If I use V-rescale thermostat, what artifacts will the simulation get
> >>> > if
> >>> I
> >>> > use a large coupling time (say, 500 ps) and single precision gromacs
> ?
> >>> >
> >>> > Thank you.
> >>> > --
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