Hi all,

I hope my mail will reach many polymer simulation experts who can guide me

out of my confusion.

This query is regarding the equivalence of reduced density and real density

and the effect of its difference on polymer property like entanglement

length.

I am modeling Polyethylene using full atomistic model rather than coarse

grained one.

Generally, the polymer simulation community working with coarse grained

simulations prefers reduced density values of 0.85 and using same they reach

various entanglement length values of these systems.

For my PE system e.g. if I have the following parameters:

N (No of atoms in simulation box) = 9500, LJ_sigma = 4.28 Angstrom,

Box_length (corresponding to real density of 0.77 grms/cc) = 65.74 Angstrom.

Then, the equivalent reduced density (rho_real) = N * LJ_sigma^3 /

Box_length^3 = 2.62

So, my query is that with this big difference in reduced density, is it

advisable to compare Entanglement length Values of two systems (coarse

grained & full atomistic)?

Other query is: why this magic number 0.85 for reduced density in coarse

grained systems?

In case, my query is bit immature then I will really appreciate if someone

can suggest me some good references!!

Thanks in advance.

Looking forward for enlightenment.