[gmx-users] Scd or -Scd?
t.piggot at soton.ac.uk
Fri Jul 14 19:46:18 CEST 2017
As far as I'm aware (and happy to be corrected if someone knows better)
it is simply a convention that stems from the fact that the signs of the
order parameters were not originally determined from experiments and so
were reported in these works as |Scd|. Given that the order parameters
of the lipid tails are pretty much always negative, it makes sense to
show -Scd to keep the plots looking the same as those that report the
absolute values of the Scd.
That said, you should be careful with reporting the absolute values
though as the order parameters (Scd) can theoretically vary between -0.5
and 1. Indeed with some force fields (e.g. ones with unsaturated double
bonds) you can have order parameters that do cross 0 (i.e. will be
plotted incorrectly if you report [Scd]).
Tom (not Justine!)
On 14/07/17 18:01, m g wrote:
> Dear Justine,Why are the order parameter data reported in articles as -S_CD (minus S_CD)?
Dr Thomas Piggot
University of Southampton, UK.
More information about the gromacs.org_gmx-users