t | float[dimensionless scalar variable] |
The parameter is not used with vsfoldX anymore, but historically,
we get
in the following way. The value obtained in McKenzie-Domb
model is
. A Gaussian distribution function would have
, and a large weight such as used in the adjusted
Jacobson-Stockmayer equation in the Turner energy rules would yield
(for
). There would be reasons to think that the
polymer exists as a reduced dimensionality meaning that t could
perhaps reduce the weight to a two-dimensional Gaussian expression
such that
. Therefore, a reasonable range for to would at most
be
. As we have argued in other places, values at
the extremes seem inappropriate at best, and values somewhere in the
middle would make the most sense.
These parameters can now be used in conjunction with Flory's polymer-solvent interaction model.
There is some appeal to using the parameter in these equations
because in the original definition of
we used only Gaussian
functions. The form of (1) has the appeal of a clean
symmetric looking function, however the meaning of the self-avoiding
walk contribution is somewhat obscured. With the MMDF model, the
parameter
is clearly suggestive of an excess volume (indeed the
expression
is an indication of a fractal volume!). We may
eventually move in the direction of using
as the defining
parameter, but because the Jacobson-Stockmayer equation used in Mfold
and the Vienna package is so common with the
, it seems
best to consider that in any discussions about parameterizations.