Dear colleagues,

I try to perform MD simulation of abstract polymer in good solvent. Particularly I try to calculate solution viscosity by means of non-equilibrium dynamics (shearing). Although shear rate is low – 0.0005 (LJ units), polymer chains longer than 30 bids become highly elongated along flow velocity vector. XX component of Rg tensor becomes 10 times larger than YY and ZZ.

Do you have any ideas, why longer chains demonstrate such behavior?

Is there theoretical relation between viscosity and Rg for such case?

Thank you, for you answers!

MD details:

LAMMPS, LJ units, repulsion only lj potential, FENE bonds for polymer, no angle potential for polymer, box size 20x20x20, total 8000 particles (density = 1), 15% of particles are attributed to polymer chains (10 to 60 particles in a chain), timestep = 0.01, nose-hoover nvt operating on ‘deform-corrected’ temperature computed by temp/deform.