gofr computation for large r values

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1

Dear Lammps Users

I have a polymer system in a disordered state. It is expected to have a long range order in MD simulations corresponding to a broader peak in g® function.

Q: If I am using LAMMPS g® compute module, the range of values I get is limited to the force cut off distance (~3 sigma). But the peak I am expecting in this case is of the order of 3Rg ~ 12 sigma. Is there is a way in LAMMPS in which I could calculate g® to values beyond force cut off?

Thanks in advance

Regards

Vaidyanathan M S

Chemical Engg, UT Austin

2

Dear Lammps Users

I have a polymer system in a disordered state. It is expected to have a long
range order in MD simulations corresponding to a broader peak in g(r)
function.

Q: If I am using LAMMPS g(r) compute module, the range of values I get is
limited to the force cut off distance (~3 sigma). But the peak I am
expecting in this case is of the order of 3Rg ~ 12 sigma. Is there is a way
in LAMMPS in which I could calculate g(r) to values beyond force cut off?

no. since it uses the non-bonded neighborlist and that is based on the
force cutoff.

the alternative would be to do the g(r) calculations as postprocessing
via the rerun command or use VMD, which does the full O(N**2) g(r) up
to sqrt(2)*box/2, if you have access to a good nvidia GPU, it may be
quite fast, even.

axel.

3

Dear Axel,

Thank you for the help. I shall try that.

Thanks and Regards

Vaidyanathan M S