Hi,
On May 11, 2006, at 6:05 PM, Arneh Babakhani wrote:
Hello,
Would the following be a reasonable way to implement semiisotropic
pressure coupling, for a 128 DMPC membrane:
; Pressure coupling is on
Pcoupl = berendsen
pcoupltype = semiisotropic
tau_p = 1.0 1.0
compressibility = 4.5e-5 1.0e-30
ref_p = 1.0 1.0
I would use slower scaling, e.g. tau_p = 10ps. The inherent
relaxation is on the order of nanoseconds anyway, so by using a too
short time you only add noise and risk risk system crashes due to
excessively hard scaling.
However, you should be aware that semi-isotropic scaling might affect
the properties if the membrane since it removes the x-y fluctuations.
On the other hand, anisotropic scaling probably over-estimates them
due to PBC.
It was a hack I introduced a long time ago when 64 lipid systems were
common, and I'm still not sure whether it's better or worse than
anisotropic scaling...
Cheers,
Erik
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