herz wrote:
It is well known that water at a surface is ordered. How do you choose
the waters to analyze? If there is a net ordering in the system due to
external factors your system is not in equilibrium, but rather in a
steady state. However if you have e.g. vacuum-water-vacuum the
symmetry makes that equipartition should hold, provided the averaging
is over a time long enough such that water molecules sample both
surfaces.
Of course if you are worried about the constraints you could do a
simulation with flexible water for testing.
"However if you have e.g. vacuum-water-vacuum the symmetry makes that
equipartition should hold, provided the averaging is over a time long
enough such that water molecules sample both surfaces."
I intended that *each* water molecule samples both surfaces...
I agree 100%! We have averaged rotational and translation kinetic energy
per water molecule for all water molecules in the system over the
complete system (vacuum, water,vacuum) over a long time (so we think we
are in equilibrum). So equipartition should hold, but it appears it
doesn't (rot energy not equipartitioned).
We have tryed with flexible water and here the problem vanishes (so
equipartition works using the same analysis!). This difference between
constraint and unconstraint water leads us to the concludion that there
is aporblem with the constraints.
But if you can not reproduce this in bulk, you still haven't proven
anything because you are changing two things at the same time.
Alex
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--
David van der Spoel, Ph.D., Professor of Biology
Molec. Biophys. group, Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone: +46184714205. Fax: +4618511755.
[email protected] [email protected] http://folding.bmc.uu.se
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