The value of PRESS in the output file is the pressure in atmospheres. Just
because you *set* PRES0=1.0 doesn't mean that your pressure will always be
1.0, it just means that's what the barostat will try to keep your pressure
at.
However, condensed phases are nearly incompressible to the point that tiny
fluctuations in volume will lead to huge fluctuations in pressure. Thus,
the values you are getting are completely expected (this point has been made
several times in the past on this list).
The value you should *actually* use is the density when possible, whose
fluctuations are far less pronounced. When you need to use pressure, I
think it's generally OK to just use the value 1 (but it depends on what
you're trying to do).
Hope this helps,
Jason
2011/8/2 zhouhaibin2008.ok <zhouhaibin2008.ok.163.com>
> Hi,All
>
> I want to use the 'PRESS' value in the sander output file , but I don't
> known what the value stand for .For example, I set the PRES0 = 1.0 in the
> sander input file , but in the output file , I find the 'PRESS' values are
> different ( like 299 , -278 ). I want to directly use 1.0 as the press value
> , ignoring other values in the output file ,is it right ?
>
> Thank you in advance!
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>
--
Jason M. Swails
Quantum Theory Project,
University of Florida
Ph.D. Candidate
352-392-4032
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Received on Tue Aug 02 2011 - 05:00:03 PDT
