[gmx-users] Re:the vapor-liquid interface of a solution at low pressure

[beibei]

Hi, all
  In fact, I want to verify the hygroscopic of lithium bromide solution, so I want to make some water moleculars in the vapor region. But I found that at 0.008bar, 303K and very small box(the unit of the length of the box is nm), there may be zero vapor moleculars. Thus I think I cannot simulate in this pressure or this temperature.  Can you give me some advice on this topic? thank you very much.
   
  Re:

Hi, beibei

The first point made by Mark is to check whether volume stabilizes when
the system is subjected to NPT simulation.

Regards,
Yang Ye

Mark Abraham wrote:
> Please leave GROMACS-related correspondence on the GROMACS mailing list.
> That way others can follow and contribute to the discussion, and it is
> archived for people to search later.
>
> Mark
>
> -------- Original Message --------
> Subject: some questions about simulate a liquid-vapor interface of a
> solution, many thanks
> Date: Thu, 12 Jun 2008 22:40:05 +0800 (CST)
> From: beibei 

> To: mark.abraham at anu.edu.au
>
>
>
> Hi, Mark
> Thank you very much to your reply. I cannot undersand some points in
> your reply. How to compute the volume that will lead to this pressure
> when the system is equilibrated? in addition, do you mean the sysytem is
> sandwich box or the cubic box?
> looking forward to your advice. Thank you very much.
> Best wishes.
>
>
> Beibei
>
> beibei wrote:
> 
>> Hi all,
>> I want to simulate the liquid-vapor interface of I lithium
>> bromide solution at 303K and 0.008bar. First I put the solution to a
>> cubic box and used NPT ensemble to simulate. Then, I enlarged the box
>> 
> to
> 
>> form two liquid-vapor interface,and used NVT ensemble, but the
>> 
> pressure
> 
>> is not 0.008 bar.
>> 
>
> You need to determine a volume that will lead to this pressure when the
> system is equilibrated. Then you need to measure for long enough to get
> a meaningful average pressure. Trial and error might be the most
> effective approach. Best of luck!
>
> 
>> If I used NPT emsemble in the second step, the box
>> becomes smaller with the run time.
>> 
>
> Of course... you won't get phase separation at equilibrium in NPT
> unless
> you happen to be at a critical point. Think about heating and cooling a
> closed and open beaker of real water.
>
> 
>> I want to know how to do when I
>> want to simulate the liquid-vapor interface of a solution at a low
>> 
> pressure.


       
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