[gmx-users] pressure for ambient water

[Amit Choubey]

Hi Justin,

Since the density (1 gm/cc) and T (300 K) correspond to ambient condition,
should not the equation of state dictate a pressure around 1 atm?

thank you
amit

On Sun, May 16, 2010 at 2:07 PM, Justin A. Lemkul <jalemkul at vt.edu> wrote:

>
>
> Amit Choubey wrote:
>
>> Hi Everyone,
>>
>> I was doing MD with SPC waters and found something which i am not sure how
>> to explain.
>>
>> I made a box of SPC water of dimension 4x4x4 nm^3 and filled with water
>> using grenbox .
>>
>> I then did a nvt simulation at 300 K for 1 ns . I used berendsen coupling
>> and Reaction - Field for coulomb interaction. Cut off were all set to 1 nm.
>> Temperature did converge to 300 K. After this i turned of nvt and did nve
>> with RF-zero for another ns. Energy was well converged during this (RMSD <
>> 0.1 %). Temperature was also around 304 K (RMSD < 1%). But the pressure was
>> 1.1 Kilobar with a fluctuation of 20 % . I don understand this, shouldnt
>> this be around 1 bar ? Could some one suggest whats on ?
>>
>>
> Since an NVE ensemble employs neither a thermostat nor a barostat, I don't
> know why you'd expect that.
>
> -Justin
>
>  Thank you,
>> amit
>>
>>
> --
> ========================================
>
> Justin A. Lemkul
> Ph.D. Candidate
> ICTAS Doctoral Scholar
> MILES-IGERT Trainee
> Department of Biochemistry
> Virginia Tech
> Blacksburg, VA
> jalemkul[at]vt.edu | (540) 231-9080
> http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
>
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