Dear Ran,
Indeed, strictly speaking a smaller time step will give you a more
precise intergration over phase-space. However, as the CG-model itself
and theirfore its corresponding energy description are parametrized
for only a certain range in time steps. The extra details which one
gains
with a more precise intergration over the energy field by chosing a
much smaller time step are beyond the actual "resolution" of the
CG-model and therefore not physical.
.........About the flip-flop problem. Please be more precize. Describe
what is a high rate in flip-flops and how long you have simulated. The
change of DOPC in cholesterol will give a dramatic change in the area
per lipid. What one sees is probably a system trying to equlibrate
itself. Does the problem still continue, after lets say 50 ns ?
Good luck,
greetings
JElger
On Thu, 06 Dec 2007 10:17:42 +0100
Ran Friedman <[EMAIL PROTECTED]> wrote:
Dear Xavier, GMX users,
Xavier Periole wrote:
One other thing. In the CG FF the time step is considered as part of
the
force field. Meaning that you should not play with it too much.
0.04-0.02 ps is the actual range where the force field is considered
to reproduce experimental values of various quantities used for
paraameterization of the FF. Outside this range you change the
balance
between the different terms and thus would alter the quality of the
FF.
Can you elaborate on this a bit? Surely if one changes the
temperature,
pressure, compressibility, threshold distances etc., one doesn't
necessarily reproduces the experimental results. Too long timesteps
may
also cause a problem. But why would it be wrong to use a shorter
time
step here?
Ran.
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