Pressure Questions

From: Rick Calloway (
Date: Wed Feb 10 2010 - 08:16:50 CST

Hi community,
Can someone help me understand the relationship between the 3 by 3 pressure
tensor ouptut on the PRESSURE: line and the single number printed under the
PRESSURE column heading on the ENERGY: line?
I assume they are both in bar so is there a tensor matrix operation that is
done on the 3x3 matrix that results in a single magnitude?
Second, when profile pressures are output the result is only a single 3
column vector. When looking for the instantaneous pressure along the
profile (like in Justin Gullingsrud's paper on Lipid Bilayer pressure
profiles) what does the 3 col vector represent and how are the normal and
lateral pressures calculated?
Lastly, the documentation between 2.6, 2.7b1 and 2.7b2 is a little
confusing as to what is included in the runtime output. When doing PME is
the profile pressure output complete or does the PME contribution to
pressure still have to be calculated from the dcd file later and added in?
Thanks for any help on these questions. My matrix algebra skills are a
little rusty so forgive me if the answers are obvious.

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