[gmx-users] Re: water genbox 3x3x0.8 EM not successful T not high

Vitaly Chaban vvchaban at gmail.com
Thu Dec 16 17:50:51 CET 2010


> From: gromacs <ptf1242 at 163.com>
> Subject: [gmx-users] water genbox 3x3x0.8 EM not successful T not high

> Hi,
>
> I want to simulate 3x3x0.8 water film (bulk water) first creat the water,
>
> genbox -cs -o film.gro -box 3 3 0.8
>
> then, i EM the bulk water;
>
> Using steep, but
>
> t = 0.011 ps: Water molecule starting at atom 298 can not be settled.
> Check for bad contacts and/or reduce the timestep.
> Wrote pdb files with previous and current coordinates
>
>
> then i run, and i get the result. I use NPT, and T=300K. I run several times, but the final T was still 411K.
>
>
>
> So what could i do to get EM process successful?
>
> And what is the reason ? why i can not control the T 300K?
>
>
>
> Energy                      Average       RMSD     Fluct.      Drift  Tot-Drift
> -------------------------------------------------------------------------------
> Potential                  -9496.38    136.145    135.455  -0.158085   -47.4256
> Kinetic En.                  2358.2    73.5876    73.5471 -0.0281891   -8.45676
> Total Energy               -7138.19    136.284    135.326  -0.186274   -55.8824
> Temperature                 411.945    12.8548    12.8477 -0.00492426   -1.47728
> Pressure (bar)             -1.66406    704.355    704.355 -0.00424907   -1.27473
> Box-X                       2.91791  0.0128965  0.0128789 -7.7826e-06 -0.00233479
> Box-Y                       2.91791  0.0128965  0.0128789 -7.7826e-06 -0.00233479
> Box-Z                      0.778108 0.00343907 0.00343437 -2.07536e-06 -0.000622609
> Density (SI)                 1038.7    13.6165    13.5998 0.00778513    2.33555
> Heat Capacity Cv:        12.49 J/mol K (factor = 0.000973754)



Hey, gromacs -

Nice to hear from you here... It is a bad idea to simulate something
with any cartesian dimension lower than a couple of nanometers using
classical FFs.  All your problems are generated by 0.8 nm of the
z-side.

--
Dr. Vitaly V. Chaban
Rochester, U.S.A.



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