[gmx-users] compression- NPT

Mark Abraham Mark.Abraham at anu.edu.au
Thu Apr 14 08:12:05 CEST 2011

On 14/04/2011 2:53 PM, Moeed wrote:
> On 13 April 2011 17:14, Mark Abraham <Mark.Abraham at anu.edu.au 
> <mailto:Mark.Abraham at anu.edu.au>> wrote:
>     On 14/04/2011 4:36 AM, Moeed wrote:
>         Hello everyone,
>         I have encountered a strange behavior while compressing a pure
>         system.
>         I am applying 100 bar pressure with PME and it turned out that
>         this pressure leads to density of 20 SI. Changing PME to SHIFT
>         compresses the system to density of above 600 SI!! and I
>         should add that PME and shift on my system give essentially
>         identical results ( I mean all those properties listed in
>         g_energy)
>     Why are you changing units of pressure mid-sentence?
> Thanks Mark. I am trying two different runs using shift and PME and 
> use the same input files..just to see the difference between these two 
> coulomb types..

For a hydrocarbon system, which is not strongly charged, it won't matter 


>         Also, when I take a configuration from a run which is
>         compressed to a higher density which is still off the desired
>         density, applying a even higher pressure in the next run not
>         only does not leads to further compression but causes the box
>         expand to a much bigger size!
>     All this sounds so wildly unlikely that you must be mismatching
>     files, or similar. Start from a fresh working directory and see
>     what you can reproduce. Extraordinary claims require extraordinary
>     evidence.
>     Mark
>     -- 
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