Test for gaussianity of chains

Dear all

This is more of a “I did, but I did not get question”. I know that this group is not intended for answering these questions and I apologize for asking. But I have been pondering over the strange condition for a long time.

I was doing a very simple test on Gaussianity of chains. I removed all pair wise interactions. It was just harmonic bonds. The equilibrated bond lengths follow the Edwards Hamiltonian (<b^2> = 3/(2k)) and 6<Rg^2> was equal to <Re^2>.
But when I calculated Rg^2, it is not coming to Nb^2/6. Is there something wrong with the way I choose the atom_modify or neigh_modify options.

Any inputs will be appreciated. Inputs are attached. I just used chain.py tool to generate input configs (tried for different N values also)

Thanks and Regards

Vaidyanathan M S

test.txt (1.15 KB)